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A systematic review of estimates of the minimal clinically important difference and patient acceptable symptom state of the Western Ontario and McMaster Universities Osteoarthritis Index in patients who underwent total hip and total knee replacement

  • C. MacKay
    Correspondence
    Address correspondence and reprint requests to: C. MacKay, West Park Healthcare Centre, Research and Evaluation, 82 Buttonwood Avenue, Toronto, ON, M6M 2J5, Canada.
    Affiliations
    West Park Healthcare Centre, Toronto, Ontario, Canada

    Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario, Canada
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  • N. Clements
    Affiliations
    Division of Health Care and Outcomes Research, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada

    The National University of Ireland, Galway, Ireland
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  • R. Wong
    Affiliations
    Division of Health Care and Outcomes Research, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
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  • A.M. Davis
    Affiliations
    Division of Health Care and Outcomes Research, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada

    Institute of Health Policy, Management and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada

    Department of Physical Therapy, University of Toronto, Toronto, Ontario, Canada

    Rehabilitation Science Institute, University of Toronto, Toronto, Ontario, Canada
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Open ArchivePublished:May 13, 2019DOI:https://doi.org/10.1016/j.joca.2019.05.002

      Summary

      Objective

      To systematically review the minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) estimates in pain and function measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients who underwent primary total knee replacement (TKR) and primary total hip replacement (THR).

      Design

      The study was carried out following PRISMA recommendations. We searched five electronic databases. Two reviewers independently screened titles, abstracts and full-text papers using a priori inclusion/exclusion criteria. Data were extracted by two independent reviewers. Data were synthesized, with WOMAC values converted to 0–100 scores (0 = best, 100 = worst).

      Results

      Thirteen studies were included. Research methods used to calculate MCIDs and PASS varied across studies (e.g., using anchor-based or distribution methods, wording of anchor questions within anchor-based methods). Baseline WOMAC scores also varied across studies. Across studies and methods, MCIDs for the WOMAC in patients undergoing TKR ranged from 13.3 to 36.0 for pain and 1.8–33.0 for function; values for WOMAC in THR ranged from 8.3 to 41.0 for pain and from 9.7 to 34.0 for function. PASS cut-offs for TKR ranged from 25.0 to 28.6 for pain and 32.3–36.7 for function, and cut-offs for THR from 15.0 to 30.6 for pain and 28.0–42.0 for function.

      Conclusion

      Although the WOMAC is a commonly used measure for a single condition, the variability in methods used to calculate MCID and PASS estimates results in a range of values across studies making it unclear whether values reported in the literature can be applied with confidence. Future research is needed to refine methods used to calculate MCIDs and PASS.

      Keywords

      Introduction

      Patient reported outcome measures (PROMs) are measures developed to assess health outcomes from the patient's perspective. They are increasingly used to measure the effectiveness of treatments in clinical research, to inform clinical decision making and patient care, and to inform health policies
      • Black N.
      Patient reported outcome measures could help transform healthcare.
      . However, the interpretability of PROMs can be difficult (e.g., interpreting the meaning of a pain reduction of two points). In order to interpret clinically important changes in outcomes, methods have been developed to determine if a medical intervention improves perceived outcomes in patients. The minimal clinically important difference (MCID) is defined according to the patient's perspective of what change is improvement
      • Engel L.
      • Beaton D.E.
      • Touma Z.
      Minimal clinically important difference: a review of outcome measure score interpretation.
      . The MCID was first defined by Jaeschke as “the smallest difference in score in the domain of interest which patients perceive as beneficial and which would mandate, in the absence of troublesome side effects and excessive cost, a change in the patient's management”
      • Jaeschke R.
      • Singer J.
      • Guyatt G.H.
      Measurement of health status. Ascertaining the minimal clinically important difference.
      . While a number of definitions of a MCID have been documented in the literature, the common thread is that the MCID represents a lower boundary of change that has been defined to be important
      • Beaton D.E.
      • Boers M.
      • Wells G.A.
      Many faces of the minimal clinically important difference (MCID): a literature review and directions for future research.
      . MCIDs are calculated using anchor-based methods which link the change in the outcome to an external anchor that accounts for the patient's perspective, or distribution methods which are data driven approaches that define different statistical parameters to assess clinical significance
      • Copay A.G.
      • Subach B.R.
      • Glassman S.D.
      • Polly Jr., D.W.
      • Schuler T.C.
      Understanding the minimum clinically important difference: a review of concepts and methods.
      . While there is no consensus on how to develop MCIDs, the primary approach recommended by the US Food and Drug Administration (FDA) and Outcome Measures in Rheumatology (OMERACT) is an empirical anchor-based approach
      • McLeod L.D.
      • Coon C.D.
      • Martin S.A.
      • Fehnel S.E.
      • Hays R.D.
      Interpreting patient-reported outcome results: US FDA guidance and emerging methods.
      • Wells G.
      • Anderson J.
      • Beaton D.
      • Bellamy N.
      • Boers M.
      • Bombardier C.
      • et al.
      Minimal clinically important difference module: summary, recommendations, and research agenda.
      • Wells G.
      • Beaton D.
      • Shea B.
      • Boers M.
      • Simon L.
      • Strand V.
      • et al.
      Minimal clinically important differences: review of methods.
      . Another complementary concept, the patient acceptable symptom state (PASS) has been defined as the highest level of symptoms beyond which patients consider themselves well. In other words, the PASS is the symptom state patients consider acceptable
      • Kvien T.K.
      • Heiberg T.
      • Hagen K.B.
      Minimal clinically important improvement/difference (MCII/MCID) and patient acceptable symptom state (PASS): what do these concepts mean?.
      . Despite advancement in the development of MCIDs and PASS for PROMs, there have been methodological challenges in defining clinically important change from the patients' perspective
      • Engel L.
      • Beaton D.E.
      • Touma Z.
      Minimal clinically important difference: a review of outcome measure score interpretation.
      • Beaton D.E.
      • Boers M.
      • Wells G.A.
      Many faces of the minimal clinically important difference (MCID): a literature review and directions for future research.
      .
      Osteoarthritis (OA) is a leading cause of disability world-wide and results in a significant economic burden due to health care expenditures
      • Vos T.
      • Flaxman A.D.
      • Naghavi M.
      • Lozano R.
      • Michaud C.
      • Ezzati M.
      • et al.
      Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010.
      • Menon J.
      • Mishra P.
      Health care resource use, health care expenditures and absenteeism costs associated with osteoarthritis in US healthcare system.
      . Total joint replacement (TJR) is a procedure which has been shown to improve outcomes in people with end-stage disease
      • Ethgen O.
      • Bruyere O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty. A qualitative and systematic review of the literature.
      • Vissers M.M.
      • Bussmann J.B.
      • Verhaar J.A.
      • Arends L.R.
      • Furlan A.D.
      • Reijman M.
      Recovery of physical functioning after total hip arthroplasty: systematic review and meta-analysis of the literature.
      • Kane R.L.
      • Saleh K.J.
      • Wilt T.J.
      • Bershadsky B.
      The functional outcomes of total knee arthroplasty.
      . A widely used PROM, assessing pain, function and stiffness in OA, is the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)
      • Bellamy N.
      • Buchanan W.W.
      • Goldsmith C.H.
      • Campbell J.
      • Stitt L.W.
      Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
      . A number of empirical studies across different countries have been conducted to estimate the MCID and PASS of the WOMAC in patients with OA. Yet, the variation in MCIDs and PASS between and within methodological approaches and countries is unclear. Earlier work comparing studies of a range of PROMs in rheumatology (focused on MCIDs) suggested that there is wide variation in values across studies
      • Doganay Erdogan B.
      • Leung Y.Y.
      • Pohl C.
      • Tennant A.
      • Conaghan P.G.
      Minimal clinically important difference as applied in rheumatology: an OMERACT rasch working group systematic review and critique.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Copay A.G.
      • Eyberg B.
      • Chung A.S.
      • Zurcher K.S.
      • Chutkan N.
      • Spangehl M.J.
      Minimum clinically important difference: current trends in the orthopaedic literature, Part II: lower extremity: a systematic review.
      limiting their utility and prompting critique of the methods used
      • Doganay Erdogan B.
      • Leung Y.Y.
      • Pohl C.
      • Tennant A.
      • Conaghan P.G.
      Minimal clinically important difference as applied in rheumatology: an OMERACT rasch working group systematic review and critique.
      . Our objective was to systematically review the evidence regarding reported MCID and PASS estimates in pain and function measured using the WOMAC in patients who underwent primary total knee replacement (TKR) and primary total hip replacement (THR).

      Methods

      Womac

      The WOMAC has demonstrated reliability, validity and responsiveness in patients with OA
      • Ethgen O.
      • Bruyere O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty. A qualitative and systematic review of the literature.
      • Bellamy N.
      • Buchanan W.W.
      • Goldsmith C.H.
      • Campbell J.
      • Stitt L.W.
      Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
      . It is comprised of three sub-scales (24 items), including pain (5 items), stiffness (2 items) and physical function (17 items)
      • Bellamy N.
      • Buchanan W.W.
      • Goldsmith C.H.
      • Campbell J.
      • Stitt L.W.
      Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
      . Scores are converted to a 0–100 scale with higher scores representing worse pain and functional limitations.

      Search strategy

      We followed guidelines for conducting and reporting in systematic reviews including the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) Statement
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • Altman D.G.
      • Group P.
      Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • Altman D.G.
      • Group P.
      Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
      . The search strategy was developed and performed by an information specialist in collaboration with research team members (AD, RW). In order to ensure a comprehensive search of articles on MCID/PASS, we incorporated keywords used or recommended by authors who have previously published reviews on MCIDs/PASS. Five electronic databases were searched from inception of the databases: Ovid MEDLINE/Ovid MEDLINE In-Process & Other Non-Indexed Citations (1946), Ovid EMBASE (1974), EBSCO CINAHL (1981), Ovid Cochrane Database of Systematic Reviews (2005), and LILACS (unknown year). Three core sets of search terms were included: MCID/PASS, WOMAC and OA/joint arthroplasty with Boolean operators OR/AND used to link search terms within/between core sets, respectively. For example, key words were: (‘minimally/minimal/minimum clinical(ly) important difference(s)’ OR ‘MCID’ OR ‘minimally/minimal/minimum important difference(s)’ OR ‘MID’ OR ‘clinical(ly) important difference(s)’ OR ‘CID’ OR ‘minimally/minimal/minimum clinical(ly) important improvement(s)’ OR ‘MCII’ OR ‘minimally/minimal/minimum clinical(ly) important change(s)’ OR ‘MCIC’ OR ‘minimally/minimal/minimum perceptible change(s)’ OR ‘meaningful change(s)’ OR ‘smallest worthwhile effect(s)’ OR ‘minimally/minimal/minimum clinically relevant state’ OR ‘low disease state’ OR ‘PASSpatient acceptable symptom state’ etc.) AND (‘Western Ontario and McMaster Universities Osteoarthritis Index’ OR ‘WOMAC’ etc.) AND (‘osteoarthritis’ OR ‘hip arthroplasty’ OR ‘knee arthroplasty’ OR ‘hip replacement’ OR ‘knee replacement’ etc.). The full list of key words utilized in each database is reported in the Appendix. The search in databases was limited to English language and publication type only when pertinent (i.e., excluded book chapters/series, conference proceeding, and letters/notes). Due to variation in the search databases, all search terms and limits were tailored to the specific database. The initial search was conducted on 2 June 2016 and updated to 13 August 2018 to identify additional literature published after the initial search.

      Study screening and selection criteria

      Results of the database searches were imported into EndNote X7. Two reviewers (RW, NC/KS) independently screened titles, followed by abstracts, and then full-text papers using a priori inclusion/exclusion criteria. Full text papers were retrieved if they passed the preliminary screen and if the records did not contain sufficient information to establish eligibility. Papers were eligible for inclusion if the following criteria were met: 1) patients had OA of the hip or knee and undergoing primary THR or TKR and 2) MCID or PASS estimates were calculated for WOMAC pain and function for THR and TKR patients separately. Papers were excluded if: 1) patient diagnosis other than OA; 2) patient population other than adults; 2) unicompartmental, bilateral or revision TKR/THR or another surgery other than TKR/THR; 3) a calculated MCID/PASS for an outcome measure other than WOMAC; 4) a calculated MCID/PASS for WOMAC but could not isolate to TKR or THR patients; 5) language other than English; and, 6) not original research (reviews/systematic reviews editorials, commentaries, workshop summaries, protocols, etc.). For papers that did not meet eligibility for final inclusion but cited or discussed an MCID/PASS estimate, the reference lists were searched to identify the primary sources of the MCID/PASS values reported and other relevant citations not generated from the database searches. Any discrepancies throughout the screening process were resolved through discussion and consensus was achieved by consulting a third reviewer (AD) as necessary.

      Data abstraction

      A data abstraction form was developed and pilot tested by team members (AD, RW, NC) using a randomly selected set of three eligible papers. Two independent reviewers (NC, CM) extracted information including study and patient characteristics, details about the primary outcome of interest (e.g., WOMAC version and scoring), the MCID and PASS definition adopted, and approach used to compute MCID or PASS values (e.g., distribution-versus anchor-based) including anchor properties, approach criteria, etc. where applicable. When a third reviewer (AD) compared the two extractions, minimal inconsistencies were found and were rectified through discussion.
      We completed the Interpretability box of the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist for all studies
      • Mokkink L.B.
      • Terwee C.B.
      • Patrick D.L.
      • Alonso J.
      • Stratford P.W.
      • Knol D.L.
      • et al.
      The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: an international Delphi study.
      . Interpretability is considered an important characteristic of a measurement instrument
      • Mokkink L.B.
      • Terwee C.B.
      • Patrick D.L.
      • Alonso J.
      • Stratford P.W.
      • Knol D.L.
      • et al.
      The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: an international Delphi study.
      and the COSMIN checklist has been used to facilitate interpretation of measures in other research
      • Hojgaard P.
      • Klokker L.
      • Orbai A.M.
      • Holmsted K.
      • Bartels E.M.
      • Leung Y.Y.
      • et al.
      A systematic review of measurement properties of patient reported outcome measures in psoriatic arthritis: a GRAPPA-OMERACT initiative.
      . We added two columns pertaining to whether each study specified anchor or distribution methods in deriving MCID/PASS values (no/yes) and rational for the method/cut points used (no/yes). These items refer to the reporting of information to facilitate interpretation of scores, rather than standards to assess risk of bias of a study on interpretability
      • Mokkink L.B.
      • de Vet H.C.W.
      • Prinsen C.A.C.
      • Patrick D.L.
      • Alonso J.
      • Bouter L.M.
      • et al.
      COSMIN risk of bias checklist for systematic reviews of patient-reported outcome measures.
      .

      Results

      The five database searches yielded 13,840 results (Medline 4661, Embase 7421, Cinahl 1382, CDSR 286, and LILACS 90). After duplications were removed, 9196 citations remained for preliminary screening. Screening of titles/abstracts for relevancy identified 430 potential citations from the database searches. An additional 2 records were identified through reference checking. The 432 full-text articles were screened for eligibility leading to the exclusion of 419 papers (i.e., 83 were not original research; 119 did not investigate MCID/PASS or WOMAC was not a primary outcome; 160 only cited or discussed an MCID/PASS but did not derive estimates; 29 derived MCID/PASS estimates but not for WOMAC; and, 28 calculated MCID/PASS for WOMAC but were not exclusively OA patients undergoing THR/TKR). Four studies were excluded as they did not calculate MCID/PASS for TKR and THR separately and one study was excluded as it was a secondary analysis of data from another included article. A total of 13 unique studies from final screening met the inclusion criteria and were kept for this review. The selection process is illustrated in Fig. 1. Data will be presented separately for TKR and THR. While there was some variability in use of terminology (MCID, minimally important difference, clinically important difference), we will use the term MCID.
      Fig. 1
      Fig. 1PRISMA flow diagram summarizing systematic search results and screening process.

      COSMIN checklist: interpretability

      Findings from the interpretability section of the Cosmin checklist are in Table I. Of the 13 studies included, seven reported on 1–3 of seven included COSMIN interpretability criteria
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      ; five reported on 4–5 criteria
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • Altman D.G.
      • Group P.
      Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
      ; and one reported on 6 criteria
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      . All publications reported the rationale for the method and cut points and 11 publications specified anchor or distribution method
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      .
      Table ICosmin checklist – interpretability
      AuthorPercent of missing itemsDescription of how missing items were handledDistribution of the (total) scoresPercent of responders who had the lowest (total) possible scorePercent of responders who had the highest (total) possible scoreScores and change scores (i.e., Means and SD) for relevant (sub) groupsSpecifies anchor or distribution methodRationale for method/cut pointsMCID or PASS determined
      Chesworth B, Mahomed N, Bourne R, Davis AM, OJRR Study group
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      noYesYesYesYesyesyesyesMCID
      Escobar A, Quintana JM, Bilbao A, Arostegui I, Lafuente I, Vidaurreta I.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      noNoyesyesYesNoYesyesMCID
      Escobar A, Perez LG, Herrera-Espineira, Aizpuru F, Sarasqueta C, Conzalez Saenz de Tejada M, Quintana JM, Bilbao A.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      nonoyesnononoyesyesMCID
      Escobar A, Gonzalez M, Quintana JM, Vrotsou K, Bilbao A, Herrera-Espineira, Garcia-Perez L, Aizpuru F, Sarasqueta C.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      nonoyesnonoyesyesyesPASS
      Vogl M, Wilkesmann R, Lausmann C, Hunger M, Plotz W
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      nonoyesnonoyesyesyesPASS
      Quintana JM, Aguirre U, Barrio I, Orive M, Garcia S, Escobar A
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      nonoyesnonoyesyesyesMCID, PASS
      Quintana J, Escobar A, Arostegui I, Bilbao A, Azkarate J, Goenaga J, Arenaza J
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      nonononononoyesyesMCID
      Maratt JD, Lee YL, Lyman S, Westrich GH
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      yesyesyesnononoyesyesMCID
      Judge A, Cooper C, Williams S, Dreinhoefer K, Dieppe P
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      yesyesyesnonoyesyesyesMID and MCID
      Quintana JM, Escobar A, Bilbao A, Arostegui I, Lafluente I, Vidaurreta I
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      nonoyesyesyesnoyesyesMCID
      Terwee CB, Roorda LD, Dekker J, Bierma-Zeinstra SM, Peat G, Jorda KP, Croft P, de Vet HCW
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      nonononononoyesyesMIC
      Naal F, Impellizzeri F, Lenze U, Wellauer V, Eisenhart-Rothe R, Leunig M
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      nononononononoyesPASS
      Vina ER, Hannon MJ, Kwoh CK
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      noyesyesnonoyesnoyesMID

      MCID and PASS for TKR

      A combined total of 7233 individuals who had TKR participated in 9 cohort studies (8 prospective and one retrospective cohort)
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      . The mean age of individuals was greater than 65 in all studies. Overall mean pre-operative pain scores ranged from 45.1 (17.3) to 64.3 (19.1) and function ranged from 45.7 (17.4) to 65.3 (17.7) (0–100 scale in which 100 is worse). Studies reported on data from TKR cohorts in six countries: Spain (n = 4), Germany (n = 1), Netherlands (n = 1), Switzerland (n = 1), Canada (n = 1) and the United States (n = 2) (some studies included cohorts from > one country). Nine studies used anchor-based methods
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      and two used distribution methods
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      (Table II summarizes the characteristics of the studies using anchor-based methods and distribution methods).
      Table IICharacteristics of studies by method (anchor-based and distribution) and country for total knee replacement (TKR)
      AuthorYearCountryParticipantsDiagnosisStudy DesignSettingTime PointsAnchor PropertiesApproachPre-op WOMAC Pain mean (SD)Pre-op WOMAC Function mean (SD)
      Studies Using Anchor-Based Methods by Country for TKR
      Chesworth et al.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      2008CanadaN = 1578; mean age 69.6; 62% femaleOAProspective cohort studyHospital setting (Ontario Joint Replacement Registry)Decision for surgery and 1 year after surgery15 point scale: −7 to +7 (0 = same; 7 = a very great deal better and −7 = a very great deal worse)ROC curves58
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      62
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      Escobar et al.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      2007Basque Country, SpainN = 516; mean age 71.6; 75% femaleOAProspective study3 hospitalsPre-TKR, 6 months and 2 years5 point scale: “a great deal better” to “a great deal worse"Mean change score for those who were “somewhat better” at 6 months or 2 years55.56 (18.53)61.87 (17.75)
      Escobar et al.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      2013SpainCohort 1: N = 415; mean age 71.4; 71.3% female

      Cohort 2: N = 497; mean age 71.4; 69.4% female
      OA2 prospective cohortsCohort 1: public hospitals cohort 2: 15 hospitalsBaseline and 12 months after surgery5 point scale: “a great deal better” to “a great deal worse”Mean change score for those who were “somewhat better”; ROC approach and 2 questions about satisfactionCohort 1: 55.8 (17.3)

      Cohort 2: 55.4 (18.7)
      Cohort 1: 61.7(17.3)

      Cohort 2: 61.8 (17.6)
      Escobar et al.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      2012SpainN = 510; mean age 71.4; 68.4% femaleOASecondary analysis of a prospective cohort study15 hospitalsBaseline and 1 year data used4 responses from “very satisfied” to “very dissatisfied”Responder analysis (OMERCT OARSI) and ROC analysis55.3 (18.6)61.0 (17.5)
      Quintana et al.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      2006SpainN = 792; 71.9 years; 73% womenOAProspective study5 large and 2 medium public teaching hospitalsPre-operatively and 6 months post-operative5 point scale: “a great deal better,” “somewhat better” to “a great deal worse”Mean change scores for those who were “somewhat better"Appropriate 57.94, uncertain 50.26, inappropriate 42.58Appropriate 65.42, uncertain 54.36, inappropriate 46.24
      Terwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      2010NetherlandsN = 73OACohort studyHospitalsPre-operatively and 6 monthsAnchor properties not stated but used “a little better"1. Mean change in score in the subgroup of patients who reported themselves as ‘‘a little better’‘; 2. ROCVot reportedNot reported
      Naal et al.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      2015Germany and SwitzerlandN = 233; mean age 70.6; 67.8% femaleend stage OAProspective cohort studyOne large teaching hospital and one university hospital in Germany1–2 weeks before surgery and at 3, 6 and 12 months after surgeryTwo 15-point global rating scales on change in pain and function: “very much worse” to “very much better”Receiver characteristic curveNot reportedNot reported
      Vina et al.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      2016USAN = 269; mean age 67.6 years; 61% femaleOA/high risk for knee OAProspective cohort study4 OAI clinical centresBefore TKR; t+1 (first follow up after TKR - any time after day 1 to 1 year after T0) and T+2 (second follow-up after TKR 1 year following T+1)original research used anchor methodPASS defined as the value beyond which patients consider themselves satisfied with actual OA symptoms (WOMAC pain <32.4 WOMAC disability <31.0): MID: 1/2 SD of difference between change scores64.3 ± 19.165.3 ± 17.7
      Maratt et al.
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      2015USAN = 2350; mean age 66.7; 57.1% femaleOARetrospective review of prospectively collected data (from hospital's data for all TKA)HospitalBaseline and 2 years6 point scale: “more improvement than I ever dreamed” to “the quality of my life is worse”ROC analysis to determine cut points using Youden index45.1 ± 17.345.7 ± 17.4
      Studies Using Distribution-Based Methods by Country for TKR
      Vina et al.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      2016USAN = 269; mean age; 67; 61% femaleOA/high risk for knee OAProspective cohort study4 OAI clinical centresBefore TKR; t+1 (first follow up after TKR - any time after day 1 to 1 year after T0) and T+2 (second follow-up after TKR 1 year following T+1)Not applicable1/2 SD of difference between change scores64.3 ± 19.165.34 ± 17.7
      Terwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      2010The NetherlandsN = 73OAProspective cohort studyHospitalBaseline and 6 monthsNo Applicable1/2 SD of baseline scoreNot reportedNot reported
      Studies (n = 9) using anchor-based methods calculated mean change scores or receiver operating curves (ROCs) or both. There was variability in the anchor used in the studies (question, response options), with three studies using a 5-point scale
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      , two studies using a 15-point scale
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      , one study using a 4-point scale
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      and one using a 6-point scale
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      (2 studies not reported
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      ). The time frame (period to compare current health status to prior health status) was also variable: three studies collected data pre-surgery and 1 year
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      , two at 6 months only
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      , one at 2 years only
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      , and three at multiple time points
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      .
      Using anchor-based methods, the MCID for WOMAC pain calculated using mean change scores was 13.3 (0.5–26.1) in one study conducted in Holland (n = 73; calculated as mean change in score in the subgroup of patients who reported themselves as ‘‘a little better’’ on the anchor)
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      and ranged from 22.6 to 29.9 in the three studies conducted in Spain
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      . Using the ROC method, the MCIDs for WOMAC pain ranged from 20.5 to 36.0. The MCID for WOMAC function calculated using the mean change method was 1.8 (−8.3-11.9) in the Dutch study
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      and ranged from 17.67 to 33.5 in studies conducted in Spain
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      . Using the ROC method, the MCIDs for WOMAC function ranged from 22.8 to 33.0. Two studies reported on distribution methods
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      . The MCID calculated was 9.4 (summary score) in an American study
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      and 10.6 for pain and 10.0 for function in another study from Holland
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      . MCIDs are presented by method in Table III (anchor-based) and Table IV (distribution).
      Table IIIEstimates of minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) for WOMAC Pain and Function in Studies of TKR using Anchor-based Methods
      CountryAuthorYearMCID: Mean ChangeMCID: ROCPASSMCID: Mean ChangeMCID: ROCPASS
      PainFunction
      CanadaChesworth et al.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      2008Improvement: 36; deterioration: 30Improvement: 33; Deterioration: 25
      Basque CountryEscobar et al.
      • Escobar A.
      • Quintana J.M.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
      20076 months: 22.87(18.13);

      2 years: 27.98 (19.44)
      6 months - 19.01 (17.48);

      2 years: 20.84 (18.2)
      SpainEscobar et al.
      • Escobar A.
      • Garcia Perez L.
      • Herrera-Espineira C.
      • Aizpuru F.
      • Sarasqueta C.
      • Gonzalez Saenz de Tejada M.
      • et al.
      Total knee replacement; minimal clinically important differences and responders.
      2013Cohort 1: Global: 29.9 (27.1–32.6); Surgery worthwhile: 28 (23.6–32.4) Global satisfaction: 25.2 (21.9–28.5)

      Cohort 2: Global: 28.1 (25.1–31.0); Surgery worthwhile: 25.6 (21.6–29.7);

      Global satisfaction: 27.5 (23.7–31.4)
      Cohort 1: ROC global: 20.5 (20.2–20.9)

      Cohort 2: ROC global: 23.5 (23.1–23.8)
      Cohort 1: Global: 31.1 (28.3–33.9); Surgery worthwhile: 20.6 (16.4–24.8); Global satisfaction: 18.8 (15.7–21.9)

      Cohort 2: Global: 33.5 (30.9–36.0); Surgery worthwhile: 22.5 (19.0–26.1); Global satisfaction: 25.8 (22.4–29.2)
      Cohort 1: ROC global: 24.2 (23.6–24.7)

      Cohort 2: ROC global: 23.0 (22.7–23.2)
      SpainEscobar et al.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      2012Centile Approach: 25.0 (20-30); ROC 28.6 (28.2–28.9)Centile Approach: 32.3 (35.3–29.4); ROC 36.7 (36.4–37.1)
      SpainQuintana et al.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      200622.617.67
      The NetherlandsTerwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      201013.3 (0.5–26.1)29.4 (19.7–39.0)1.8 (−8.3 to 11.9)22.8 (6.2–39.4)
      Germany and SwitzerlandNaal et al.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      2015AUC
      PASS for pain and function not presented separately.
      : 6 months: 0.77 (0.68–0.85); cut-off: 30.7 12 months: AUC: 0.89 (0.82–0.96); cut-off: 12.2
      USAVina et al.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      201690.81% improved90.68% improved
      USAMaratt et al.
      • Maratt J.D.
      • Lee Y.Y.
      • Lyman S.
      • Westrich G.H.
      Predictors of satisfaction following total knee arthroplasty.
      201531.2526.93
      PASS for pain and function not presented separately.
      Table IVEstimates of MCID for WOMAC Pain and Function in Studies of TKR using Distribution Methods
      Country of ConductAuthorYearSummary ScorePainFunction
      ½ standard deviation
      USAVina et al.
      • Vina E.R.
      • Hannon M.J.
      • Kwoh C.K.
      Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
      20169.4
      0.5 SD of difference between change scores.
      NetherlandsTerwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      201010.6
      0.5 SD of the baseline score.
      10.0
      0.5 SD of the baseline score.
      0.5 SD of difference between change scores.
      0.5 SD of the baseline score.
      PASS cut-offs were calculated using the 75th centile or ROC analysis approach. Some researchers used a range of response options (4 items) to rate their satisfaction with joint replacement and others used a yes/no response option. Escobar et al.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      reported cut-offs for TKR that ranged from 25.0 to 28.6 for pain and 32.3–36.7 for function. Naal et al.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      reported PASS cut-offs for the summary WOMAC as 30.7 at 6 months and 12.2 at 12 months (Table III).

      MCID and PASS for THR

      A combined total of 5540 individuals who had undergone THR from 9 prospective cohort studies were included
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      . The mean age of individuals was greater than 65 in all studies. Pre-operative pain scores ranged from a mean of 44.4 (1.1) to 58.0
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      ; pre-operative function scores ranged from 48.7 (1.1) to 65.8 (16.97) (0–100 scale with higher scores indicating more pain and worse function). Studies were conducted in individuals undergoing THR in Canada (n = 1), Spain (n = 4), Netherlands (n = 1), Germany (n = 2), Switzerland (n = 1), and multiple countries in Europe (n = 1). Eight studies used anchor-based methods
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      and 2 used distribution methods
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      . The anchor question, response options and time frames varied across studies. Data were collected pre-surgery in all studies and at 6 months (n = 4)
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      , 1 year (n = 2)
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      and multiple time points (n = 2)
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      . Table V summarizes the characteristics of the studies using anchor-based methods and distribution methods.
      Table VCharacteristics of studies by method (anchor-based and distribution) and country for total hip replacement (THR)
      AuthorYearCountryParticipantsDiagnosisStudy DesignSettingTime PointsAnchor PropertiesMCID ApproachPre-op WOMAC Pain mean (SD)Pre-op WOMAC Function mean (SD)
      Studies Using Anchor-Based Methods by Country for THR
      Chesworth et al.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      2008CanadaN=1131; mean age 68.8; 57% femaleOAProspective cohort studyHospitalDecision for surgery and 1 year15 point scale varied from −7 to +7 (0 = same; 7 = a very great deal better and −7 = a very great deal worse)ROC curves58.0(17)62.0(17)
      Escobar et al.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      2012SpainN=351; 44.3% female; mean age 65.4OASecondary analysis of a prospective cohort study15 hospitalsBaseline and 1 year4 response options from “very satisfied” to “very dissatisfied”PASS: Responder analysis (OMERCT OARSI) and ROC analysis55.2(17.4)64.9(16.5)
      Quintana et al.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      2012Basque Country; SpainCohort 1: N=573; 51.8% female; 48.5% > age 70

      Cohort 2: N=333;

      48.1% female; 48.8% > age 70
      OA2 prospective cohorts7 teaching hospitalsPreoperative and 6 months“If you had to live the rest of your life with the hip symptoms you have now, how would you feel?” Response: “totally satisfied”, “slightly satisfied”, “not satisfied”, and “not at all satisfied”; Cohort 1 only: “Compared with status before you had a hip prosthesis how would you rate the status of your hip right now?” 7 responses from “a great deal better” to “a great deal worse”PASSTotal: 55.62(19.05)

      Cohort 1: 54.3(18.57)

      Cohort 2: 57.8(19.58)
      Total: 65.80(16.97)

      Cohort 1:

      64.39(16.86)

      Cohort 2: 68.0(16.98)
      Quintana et al.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      2006SpainN=784; 48% female; mean age 69.1OAProspective cohort study5 large and 2 medium public teaching hospitalsPreoperative and 6 monthsQuestion about joint improvement; five response options: “a great deal better” to “a great deal worse.”Change scores calculated for “somewhat better”appropriate - 59.61; uncertain 42.23; inappropriate 27.08; knees appropriateappropriate - 69.62, uncertain 55.58, inappropriate 42.92
      Quintana et al.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      2005Basque CountryN=379 at 6 months and 310 at 2 years; 50.7% female, mean age 69.4 (8.8)OAProspective cohort study3 teaching hospitalsPreoperative, 6 months and 2 yearsTransitional question about joint improvement with five response options from “a great deal better” to “a great deal worse”Change for those who responded “somewhat better"54.68 (18.71)64.73 (16.27)
      Terwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      2010The NetherlandsN=188OAProspective cohort studyHospitalBaseline and 6 monthsAnchor properties not stated1. Mean change in score in the subgroup of patients who reported themselves as ‘‘a little better’’ on the anchor; 2. ROCNot reportedNot reported
      Naal et al.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      2015Germany and SwitzerlandN=193; Mean age 66.1; 48.2% femaleOAProspective cohort studyOne large teaching hospital in Switzerland and one university hospital in GermanyPre-surgery, 3, 6, 12 monthsTwo 15-point global rating scales, indicating whether they had changed in pain and physical functioning (“very much worse” to “very much better”)PASS: ROC (cut off based on Youden index)Not reportedNot reported
      Vogl et al.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      2014GermanyN=281; 58% female; mean age 68OA and osteonecrosisProspective cohort studyClinicBaseline and 6 monthsWere your expectations on THR fulfilled?PASS (75%); ROC44.4 (1.1)48.7(1.1)
      Studies Using Distribution-Based Methods by Country for THR
      Terwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      2010The NetherlandsN=188OAProspective cohort studyHospitalBaseline and 6 monthsNot applicable1/2 SD of baseline scoreNot reportedNot reported
      Judge at al.
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      201012 countries in EuropeN=1327 at baseline; 908 completed 12 months; 56% female, Age:<50 = 77 (8.6). 50–69 = 486 (54.3), >=70 (37.1)OAProspective cohort study20 orthopaedic centresBaseline and 12 monthsNot applicable½ SD mean difference in WOMAC measurements54.5 ± 17.658.7 ± 16.3
      Using anchor-based methods, the MCID for WOMAC pain calculated using mean change scores was 8.3 in one study from Holland
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      . In Spain, values ranged from 24.55 to 29.26 in three studies (with one study reporting cut-offs of 15, 23, 36 for 1, 2 and 3 baseline tertile scores, respectively)
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      . Using the ROC method, the MCIDs for WOMAC pain ranged from 22.4 to 41.0. For function, the MCID, using the mean change method ranged from 20.8 to 26.54. Using the ROC method, the MCID ranged from 18.4 to 34.0. Using distribution methods, MCIDs were calculated as 10.5 for pain and 9.7 for function in one study
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      and reported in another study as a difference in pain score of ≥24.5 and in function score of ≥ 23.9
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      . MCIDs are presented by approach in Table VI, Table VII.
      Table VIEstimates of MCID and PASS for WOMAC Pain and Function in Studies of THR using Anchor-based Methods
      CountryAuthorYearMCID: Mean changeMCID: ROCPASSMCID: Mean changeMCID: ROCPASS
      PainFunction
      CanadaChesworth et al.
      • Chesworth B.M.
      • Mahomed N.N.
      • Bourne R.B.
      • Davis A.M.
      • Group O.S.
      Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
      2008CID improvement: 41; CID deterioration: 35CID improvement: 34; CID deterioration: 33
      SpainEscobar et al.
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      2012Centile approach: 20.0; ROC: 30

      AUC: 0.77 (0.70–0.84)
      Centile approach: 30.9; ROC: 31.2

      AUC: 0.81 (0.75–0.87)
      Basque Country, SpainQuintana et al.
      • Quintana J.M.
      • Aguirre U.
      • Barrio I.
      • Orive M.
      • Garcia S.
      • Escobar A.
      Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
      201215, 23, 36 for tertiles19, 25, 25

      Validation cohort: 20, 25, 25
      20, 25 and 25 for tertiles

      Validation cohort: 20, 25, 25
      9, 22 and 31 for tertiles26.4, 39, 40

      Validation cohort: 25, 39, 40
      28, 35 and 42 for tertiles

      Validation cohort: 32, 32, 40
      SpainQuintana et al.
      • Quintana J.M.
      • Escobar A.
      • Arostegui I.
      • Bilbao A.
      • Azkarate J.
      • Goenaga J.I.
      • et al.
      Health-related quality of life and appropriateness of knee or hip joint replacement.
      200624.5520.8
      Basque Country, SpainQuintana et al.
      • Quintana J.M.
      • Escobar A.
      • Bilbao A.
      • Arostegui I.
      • Lafuente I.
      • Vidaurreta I.
      Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
      200529.26 (16.9)26.54 (17.79)
      NetherlandsTerwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      20108.3 (−0.3 to 16.9)22.4 (2.5–42.3)23.7 (11.1–36.3)18.4 (2.9–39.6)
      Germany and SwitzerlandNaal et al.
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      20156 months AUC: 0.92 (0.85–0.98); cut-off: 15.4

      12 months AUC: 0.84 (0.70–0.98); cut-off: 14.4
      PASS for pain and function not presented separately.
      GermanyVogl et al.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      2014Estimates above 15 for global WOMAC; of patients who considered state satisfactory 75% had a change in WOMAC of >25
      PASS for pain and function not presented separately.
      PASS for pain and function not presented separately.
      Table VIIEstimates of MCID for WOMAC Pain and Function in Studies of THR using Distribution Methods
      CountryAuthorYearPainFunction
      ½ Standard Deviation
      NetherlandsTerwee et al.
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      ,
      0.5 SD of the baseline score.
      201010.59.7
      EuropeJudge et al.
      • Judge A.
      • Cooper C.
      • Williams S.
      • Dreinhoefer K.
      • Dieppe P.
      Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
      ,
      0.5 SD of mean difference in scores.
      2010≥24.5
      As reported.
      ≥23.9
      As reported.
      0.5 SD of the baseline score.
      0.5 SD of mean difference in scores.
      As reported.
      PASS cutoffs were calculated using the 75th centile or ROC method. The number of response options on the question of satisfaction varied (4 or 10 options). The cut-off for pain was reported as 20.0 and 30.0 in one study using different methods (percentile and ROC approach, respectively) and 30.9 and 31.2 for function
      • Escobar A.
      • Gonzalez M.
      • Quintana J.M.
      • Vrotsou K.
      • Bilbao A.
      • Herrera-Espineira C.
      • et al.
      Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
      . Two studies reported that PASS values for summary WOMAC scores were close to 15
      • Naal F.D.
      • Impellizzeri F.M.
      • Lenze U.
      • Wellauer V.
      • von Eisenhart-Rothe R.
      • Leunig M.
      Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      (Table VI).

      Discussion

      In this systematic review the estimates of the MCIDs and PASS for pain and function were examined for a commonly used measure, the WOMAC, and in the context of a specific procedure for end stage OA i.e., primary THR and TKR. The derived MCID and PASS values from the 13 studies included were variable within and across countries. Across studies and methods, MCIDs for the WOMAC in patients undergoing TKR ranged from 13.3 to 36.0 for pain and 1.8–33.0 for function; values for WOMAC pain in THR ranged from 8.3 to 41.0 for pain and from 9.7 to 34.0 for function.
      Previous studies have reported significant heterogeneity in the calculation methods used for MCIDs in rheumatology
      • Doganay Erdogan B.
      • Leung Y.Y.
      • Pohl C.
      • Tennant A.
      • Conaghan P.G.
      Minimal clinically important difference as applied in rheumatology: an OMERACT rasch working group systematic review and critique.
      • Copay A.G.
      • Eyberg B.
      • Chung A.S.
      • Zurcher K.S.
      • Chutkan N.
      • Spangehl M.J.
      Minimum clinically important difference: current trends in the orthopaedic literature, Part II: lower extremity: a systematic review.
      . While we found variation in methodological approaches to determining the MCID (anchor and distribution approaches as expected) and the PASS, we also found variation within a given method (e.g., different wording of anchor questions and choice of cut-points). Additionally, there was variation in patient sample characteristics (i.e., baseline WOMAC scores) used to determine values and, given the known influence of baseline scores on MCID and PASS calculations
      • Engel L.
      • Beaton D.E.
      • Touma Z.
      Minimal clinically important difference: a review of outcome measure score interpretation.
      • Beaton D.E.
      • Boers M.
      • Wells G.A.
      Many faces of the minimal clinically important difference (MCID): a literature review and directions for future research.
      , this likely also contributed to the variability in the values obtained.
      Using the COSMIN interpretability questions, we found that seven of 13 studies reported on only 1–3 COSMIN criteria. While interpretability is not a measurement property, these questions are intended to facilitate interpretation of the scores
      • Mokkink L.B.
      • Terwee C.B.
      • Patrick D.L.
      • Alonso J.
      • Stratford P.W.
      • Knol D.L.
      • et al.
      The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: an international Delphi study.
      • Mokkink L.B.
      • de Vet H.C.W.
      • Prinsen C.A.C.
      • Patrick D.L.
      • Alonso J.
      • Bouter L.M.
      • et al.
      COSMIN risk of bias checklist for systematic reviews of patient-reported outcome measures.
      . Lack of reporting in a number of studies highlight limitations in interpreting findings from these studies and points to the need for better reporting in MCID/PASS studies in the future (e.g., percentage of responders with lowest possible score, highest possible score and score in sub-groupings).
      It is generally accepted that a PROM like the WOMAC would not have a single MCID and that values for the MCID would vary depending on the intervention and context (e.g., patient group)
      • King M.T.
      A point of minimal important difference (MID): a critique of terminology and methods.
      • Davis A.M.
      • Perruccio A.V.
      • Lohmander L.S.
      Minimally clinically important improvement: all non-responders are not really non-responders an illustration from total knee replacement.
      . Interestingly, even within the context of one intervention with a relatively predictable result in a population with end stage OA, we found that there is heterogeneity in the approaches used to calculate MCIDs for the WOMAC in patients undergoing TJR and subsequent values for the MCID. In this review, more studies used anchor-based methods compared to distribution methods as recommended
      • McLeod L.D.
      • Coon C.D.
      • Martin S.A.
      • Fehnel S.E.
      • Hays R.D.
      Interpreting patient-reported outcome results: US FDA guidance and emerging methods.
      • Wells G.
      • Anderson J.
      • Beaton D.
      • Bellamy N.
      • Boers M.
      • Bombardier C.
      • et al.
      Minimal clinically important difference module: summary, recommendations, and research agenda.
      • Wells G.
      • Beaton D.
      • Shea B.
      • Boers M.
      • Simon L.
      • Strand V.
      • et al.
      Minimal clinically important differences: review of methods.
      . However, there was variation within methods, which included: 1) variation in the wording of the anchor question and the response scale (e.g., in TKR, anchors ranged from a 4-point scale to a 15-point scale), 2) the time frame studied, and 3) the approach to calculating the MCID (mean change and ROC). First, MCID was more often calculated for patients reported to be “somewhat better” in the anchor response but cutoffs varied (e.g., patients reporting to be “a little better”). While the cutoff is paramount to defining small but important change, there is a lack of evidence and agreement to optimal cutoff levels
      • Engel L.
      • Beaton D.E.
      • Touma Z.
      Minimal clinically important difference: a review of outcome measure score interpretation.
      . Some have suggested that the validity of anchors could be improved by querying about the importance of change rather than using the magnitude of change item
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      . Moreover, patients may need to be involved in specifying the cut-point to be used, rather than the investigator/clinician as often occurs. Variation also included the time frame for the study (e.g., baseline and 6 months, 12 months, 2 years). Since studies have demonstrated that much of the change in pain and function occurs within the first 6 months following TJR
      • Davis A.M.
      • Perruccio A.V.
      • Lohmander L.S.
      Minimally clinically important improvement: all non-responders are not really non-responders an illustration from total knee replacement.
      • Lenguerrand E.
      • Wylde V.
      • Gooberman-Hill R.
      • Sayers A.
      • Brunton L.
      • Beswick A.D.
      • et al.
      Trajectories of pain and function after primary hip and knee arthroplasty: the ADAPT cohort study.
      it is likely the studies reporting on 6 and 12 months are most relevant as change beyond this time period may be influenced by external contextual factors or events. In other research, 36% of patients who underwent THR reported one or more positive impact life events in the year following surgery, while 63% reported one or more negative life events. The number of positive life events was associated with engagement in life activities following THR
      • MacKay C.
      • Webster F.
      • Venkataramanan V.
      • Bytautas J.
      • Perruccio A.V.
      • Wong R.
      • et al.
      A prospective cohort study examining medical and social factors associated with engagement in life activities following total hip replacement.
      . Finally, not all studies conducted a ROC analysis. This is despite recommendations that ROC methods be used for values that are to be applied at the individual level
      • Terwee C.B.
      • Roorda L.D.
      • Dekker J.
      • Bierma-Zeinstra S.M.
      • Peat G.
      • Jordan K.P.
      • et al.
      Mind the MIC: large variation among populations and methods.
      . Overall, there appeared to be variability in values regardless of method used.
      We found there was significant variation in the baseline WOMAC pain and function scores across studies for the same intervention. While TJR is a procedure for end-stage OA, this is not surprising as there are no agreed upon guidelines on surgical candidacy for TJR. There is evidence of large heterogeneity in patient status at the time of surgery and pain and function alone do not determine who may be a surgical candidate
      • Dieppe P.
      • Judge A.
      • Williams S.
      • Ikwueke I.
      • Guenther K.P.
      • Floeren M.
      • et al.
      Variations in the pre-operative status of patients coming to primary hip replacement for osteoarthritis in European orthopaedic centres.
      • Ackerman I.N.
      • Dieppe P.A.
      • March L.M.
      • Roos E.M.
      • Nilsdotter A.K.
      • Brown G.C.
      • et al.
      Variation in age and physical status prior to total knee and hip replacement surgery: a comparison of centers in Australia and Europe.
      • Gademan M.G.
      • Hofstede S.N.
      • Vliet Vlieland T.P.
      • Nelissen R.G.
      • Marang-van de Mheen P.J.
      Indication criteria for total hip or knee arthroplasty in osteoarthritis: a state-of-the-science overview.
      . Variation in baseline scores has been found across other studies of MCIDs and researchers have highlighted the influence of baseline scores on the value calculated in studies of MCIDs
      • Engel L.
      • Beaton D.E.
      • Touma Z.
      Minimal clinically important difference: a review of outcome measure score interpretation.
      • Beaton D.E.
      • Boers M.
      • Wells G.A.
      Many faces of the minimal clinically important difference (MCID): a literature review and directions for future research.
      • de Vet H.C.
      • Terwee C.B.
      The minimal detectable change should not replace the minimal important difference.
      . Davis et al.
      • Davis A.M.
      • Perruccio A.V.
      • Lohmander L.S.
      Minimally clinically important improvement: all non-responders are not really non-responders an illustration from total knee replacement.
      showed that failure to consider baseline scores could result in some patients being misclassified as having not benefitted from treatment (some patients could not achieve important improvement due to baseline scores). Some researchers have studied the use of item response theory-informed methods to correct for the variability in MCID based on baseline score
      • Rouquette A.
      • Blanchin M.
      • Sebille V.
      • Guillemin F.
      • Cote S.M.
      • Falissard B.
      • et al.
      The minimal clinically important difference determined using item response theory models: an attempt to solve the issue of the association with baseline score.
      but the limited evidence to date does not provide information on what methods are superior in developing MCIDs.
      Studies were included from a range of countries. Studies conducted in Spain were most common and used similar methods (i.e., anchor-based, mean change). While the variability within studies conducted in Spain was less than across methods and countries, there was heterogeneity in results particularly for THR (TKR: 22.6–29.9; THR: 17.67–33.5). These findings further highlight the challenges inherent when determining and interpreting important change.
      Fewer studies were included which calculated a PASS for WOMAC pain and function for patient undergoing TJR. Studies used ROC curves or the 75th centile approach (75th percentile of the scores for improvement in patients who report an important improvement by the anchoring question). PASS cut-offs were similar across the studies of TKR (25.0–28.6 for pain; 32.3–36.7 for function). While there were few findings reported for PASS for THR, values ranged from 20.0 to 30.0 for pain and 30.9–31.2 for function. Vogl et al.
      • Vogl M.
      • Wilkesmann R.
      • Lausmann C.
      • Hunger M.
      • Plotz W.
      The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
      reported a summary WOMAC score of 15 and interpreted that their low threshold state compared to other studies conducted in THR was because the cohort had lower baseline and follow-up scores. Similar to MCIDs, researchers have suggested that the methodology for identification of PASS may influence the identified cut-off points. The ROC approach has provided estimates that were somewhat lower than the cut-off points identified with the 75th centile approach
      • Kvien T.K.
      • Heiberg T.
      • Hagen K.B.
      Minimal clinically important improvement/difference (MCII/MCID) and patient acceptable symptom state (PASS): what do these concepts mean?.
      . This was not evident from the few studies included in this systematic review.
      The study has limitations. Publications in languages other than English were not included. Findings are specific to the study population and are nontransferable across patient groups or interventions. Despite a comprehensive search strategy to locate articles, it is possible studies meeting inclusion/exclusion criteria were missed.
      The WOMAC is a commonly used PROM in patients undergoing TJR. Yet, our findings highlight variation in methodological approaches used to determine MCIDs and PASS for the WOMAC, variation in approaches within methods, and variation in patient sample characteristics used to determine values. Due to the heterogeneity in the research methods used across studies, we were unable to identify clear patterns (e.g., participant characteristics or methodological approaches) that may explain the heterogeneity in estimates. Given the variability in the values reported for MCID and PASS across studies it is unclear that the values reported in the current literature can be applied to new research with confidence. To be able to use PROMs and identify responders to interventions, more standardization of methodological approaches to estimating MCIDs and PASS (including methods within approaches i.e., anchor questions) may be required. This standardization will be critical in the era of personalized medicine in which therapies are targeted to sub-groups of patients with unique attributes. At present, careful consideration needs to be given to the applicability of a given MCID to the specific context in which the WOMAC will be used. Future research is needed to refine methods used to calculate MCIDs and PASS including comparative methods research.

      Author contributions

      Conception and design: Davis.
      Data acquisition: Clements, Wong.
      Analysis and interpretation of the data: MacKay, Clements, Wong, Davis.
      Drafting of the article: MacKay.
      Critical revision of the article for important intellectual content: Clements, Wong, Davis.
      Final approval of the article: MacKay, Clements, Wong, Davis.
      Dr. Davis ([email protected]) takes responsibility for the integrity of the work as a whole.

      Competing interests

      None of the authors have any conflicts of interests in relation to this work.

      Role of the funding source

      There was no role of a funding agency in this work.

      Appendix A. Supplementary data

      The following is the supplementary data to this article:

      References

        • Black N.
        Patient reported outcome measures could help transform healthcare.
        BMJ. 2013; 346: f167
        • Engel L.
        • Beaton D.E.
        • Touma Z.
        Minimal clinically important difference: a review of outcome measure score interpretation.
        Rheum Dis Clin N Am. 2018; 44: 177-188
        • Jaeschke R.
        • Singer J.
        • Guyatt G.H.
        Measurement of health status. Ascertaining the minimal clinically important difference.
        Contr Clin Trials. 1989; 10: 407-415
        • Beaton D.E.
        • Boers M.
        • Wells G.A.
        Many faces of the minimal clinically important difference (MCID): a literature review and directions for future research.
        Curr Opin Rheumatol. 2002; 14: 109-114
        • Copay A.G.
        • Subach B.R.
        • Glassman S.D.
        • Polly Jr., D.W.
        • Schuler T.C.
        Understanding the minimum clinically important difference: a review of concepts and methods.
        Spine J. 2007; 7: 541-546
        • McLeod L.D.
        • Coon C.D.
        • Martin S.A.
        • Fehnel S.E.
        • Hays R.D.
        Interpreting patient-reported outcome results: US FDA guidance and emerging methods.
        Expert Rev Pharmacoecon Outcomes Res. 2011; 11: 163-169
        • Wells G.
        • Anderson J.
        • Beaton D.
        • Bellamy N.
        • Boers M.
        • Bombardier C.
        • et al.
        Minimal clinically important difference module: summary, recommendations, and research agenda.
        J Rheumatol. 2001; 28: 452-454
        • Wells G.
        • Beaton D.
        • Shea B.
        • Boers M.
        • Simon L.
        • Strand V.
        • et al.
        Minimal clinically important differences: review of methods.
        J Rheumatol. 2001; 28: 406-412
        • Kvien T.K.
        • Heiberg T.
        • Hagen K.B.
        Minimal clinically important improvement/difference (MCII/MCID) and patient acceptable symptom state (PASS): what do these concepts mean?.
        Ann Rheum Dis. 2007; 66: iii40-iii41
        • Vos T.
        • Flaxman A.D.
        • Naghavi M.
        • Lozano R.
        • Michaud C.
        • Ezzati M.
        • et al.
        Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010.
        Lancet. 2012; 380: 2163-2196
        • Menon J.
        • Mishra P.
        Health care resource use, health care expenditures and absenteeism costs associated with osteoarthritis in US healthcare system.
        Osteoarthritis Cartilage. 2018; 26: 480-484
        • Ethgen O.
        • Bruyere O.
        • Richy F.
        • Dardennes C.
        • Reginster J.Y.
        Health-related quality of life in total hip and total knee arthroplasty. A qualitative and systematic review of the literature.
        J Bone Joint Surg Am. 2004; 86-A: 963-974
        • Vissers M.M.
        • Bussmann J.B.
        • Verhaar J.A.
        • Arends L.R.
        • Furlan A.D.
        • Reijman M.
        Recovery of physical functioning after total hip arthroplasty: systematic review and meta-analysis of the literature.
        Phys Ther. 2011; 91: 615-629
        • Kane R.L.
        • Saleh K.J.
        • Wilt T.J.
        • Bershadsky B.
        The functional outcomes of total knee arthroplasty.
        J Bone Joint Surg Am. 2005; 87: 1719-1724
        • Bellamy N.
        • Buchanan W.W.
        • Goldsmith C.H.
        • Campbell J.
        • Stitt L.W.
        Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
        J Rheumatol. 1988; 15: 1833-1840
        • Doganay Erdogan B.
        • Leung Y.Y.
        • Pohl C.
        • Tennant A.
        • Conaghan P.G.
        Minimal clinically important difference as applied in rheumatology: an OMERACT rasch working group systematic review and critique.
        J Rheumatol. 2016; 43: 194-202
        • Terwee C.B.
        • Roorda L.D.
        • Dekker J.
        • Bierma-Zeinstra S.M.
        • Peat G.
        • Jordan K.P.
        • et al.
        Mind the MIC: large variation among populations and methods.
        J Clin Epidemiol. 2010; 63: 524-534
        • Copay A.G.
        • Eyberg B.
        • Chung A.S.
        • Zurcher K.S.
        • Chutkan N.
        • Spangehl M.J.
        Minimum clinically important difference: current trends in the orthopaedic literature, Part II: lower extremity: a systematic review.
        JBJS Rev. 2018; 6: e2
        • Moher D.
        • Liberati A.
        • Tetzlaff J.
        • Altman D.G.
        • Group P.
        Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
        BMJ. 2009; 339: b2535
        • Moher D.
        • Liberati A.
        • Tetzlaff J.
        • Altman D.G.
        • Group P.
        Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
        PLoS Med. 2009; 6e1000097
        • Mokkink L.B.
        • Terwee C.B.
        • Patrick D.L.
        • Alonso J.
        • Stratford P.W.
        • Knol D.L.
        • et al.
        The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: an international Delphi study.
        Qual Life Res. 2010; 19: 539-549
        • Hojgaard P.
        • Klokker L.
        • Orbai A.M.
        • Holmsted K.
        • Bartels E.M.
        • Leung Y.Y.
        • et al.
        A systematic review of measurement properties of patient reported outcome measures in psoriatic arthritis: a GRAPPA-OMERACT initiative.
        Semin Arthritis Rheum. 2018; 47: 654-665
        • Mokkink L.B.
        • de Vet H.C.W.
        • Prinsen C.A.C.
        • Patrick D.L.
        • Alonso J.
        • Bouter L.M.
        • et al.
        COSMIN risk of bias checklist for systematic reviews of patient-reported outcome measures.
        Qual Life Res. 2018; 27: 1171-1179
        • Escobar A.
        • Gonzalez M.
        • Quintana J.M.
        • Vrotsou K.
        • Bilbao A.
        • Herrera-Espineira C.
        • et al.
        Patient acceptable symptom state and OMERACT-OARSI set of responder criteria in joint replacement. Identification of cut-off values.
        Osteoarthritis Cartilage. 2012; 20: 87-92
        • Escobar A.
        • Quintana J.M.
        • Bilbao A.
        • Arostegui I.
        • Lafuente I.
        • Vidaurreta I.
        Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement.
        Osteoarthritis Cartilage. 2007; 15: 273-280
        • Naal F.D.
        • Impellizzeri F.M.
        • Lenze U.
        • Wellauer V.
        • von Eisenhart-Rothe R.
        • Leunig M.
        Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients' perspective.
        Qual Life Res. 2015; 24: 2917-2925
        • Quintana J.M.
        • Aguirre U.
        • Barrio I.
        • Orive M.
        • Garcia S.
        • Escobar A.
        Outcomes after total hip replacement based on patients' baseline status: what results can be expected?.
        Arthritis Care Res. 2012; 64: 563-572
        • Quintana J.M.
        • Escobar A.
        • Arostegui I.
        • Bilbao A.
        • Azkarate J.
        • Goenaga J.I.
        • et al.
        Health-related quality of life and appropriateness of knee or hip joint replacement.
        Arch Intern Med. 2006; 166: 220-226
        • Vogl M.
        • Wilkesmann R.
        • Lausmann C.
        • Hunger M.
        • Plotz W.
        The impact of preoperative patient characteristics on health states after total hip replacement and related satisfaction thresholds: a cohort study.
        Health Qual Life Outcomes. 2014; 12: 108
        • Moher D.
        • Liberati A.
        • Tetzlaff J.
        • Altman D.G.
        • Group P.
        Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
        J Clin Epidemiol. 2009; 62: 1006-1012
        • Chesworth B.M.
        • Mahomed N.N.
        • Bourne R.B.
        • Davis A.M.
        • Group O.S.
        Willingness to go through surgery again validated the WOMAC clinically important difference from THR/TKR surgery.
        J Clin Epidemiol. 2008; 61: 907-918
        • Escobar A.
        • Garcia Perez L.
        • Herrera-Espineira C.
        • Aizpuru F.
        • Sarasqueta C.
        • Gonzalez Saenz de Tejada M.
        • et al.
        Total knee replacement; minimal clinically important differences and responders.
        Osteoarthritis Cartilage. 2013; 21: 2006-2012
        • Judge A.
        • Cooper C.
        • Williams S.
        • Dreinhoefer K.
        • Dieppe P.
        Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort.
        Arthritis Care Res. 2010; 62: 480-488
        • Maratt J.D.
        • Lee Y.Y.
        • Lyman S.
        • Westrich G.H.
        Predictors of satisfaction following total knee arthroplasty.
        J Arthroplast. 2015; 30: 1142-1145
        • Quintana J.M.
        • Escobar A.
        • Bilbao A.
        • Arostegui I.
        • Lafuente I.
        • Vidaurreta I.
        Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement.
        Osteoarthritis Cartilage. 2005; 13: 1076-1083
        • Vina E.R.
        • Hannon M.J.
        • Kwoh C.K.
        Improvement following total knee replacement surgery: exploring preoperative symptoms and change in preoperative symptoms.
        Semin Arthritis Rheum. 2016; 45: 547-555
        • King M.T.
        A point of minimal important difference (MID): a critique of terminology and methods.
        Expert Rev Pharmacoecon Outcomes Res. 2011; 11: 171-184
        • Davis A.M.
        • Perruccio A.V.
        • Lohmander L.S.
        Minimally clinically important improvement: all non-responders are not really non-responders an illustration from total knee replacement.
        Osteoarthritis Cartilage. 2012; 20: 364-367
        • Lenguerrand E.
        • Wylde V.
        • Gooberman-Hill R.
        • Sayers A.
        • Brunton L.
        • Beswick A.D.
        • et al.
        Trajectories of pain and function after primary hip and knee arthroplasty: the ADAPT cohort study.
        PLoS One. 2016; 11e0149306
        • MacKay C.
        • Webster F.
        • Venkataramanan V.
        • Bytautas J.
        • Perruccio A.V.
        • Wong R.
        • et al.
        A prospective cohort study examining medical and social factors associated with engagement in life activities following total hip replacement.
        Osteoarthritis Cartilage. 2017; 25: 1032-1039
        • Dieppe P.
        • Judge A.
        • Williams S.
        • Ikwueke I.
        • Guenther K.P.
        • Floeren M.
        • et al.
        Variations in the pre-operative status of patients coming to primary hip replacement for osteoarthritis in European orthopaedic centres.
        BMC Muscoskelet Disord. 2009; 10: 19
        • Ackerman I.N.
        • Dieppe P.A.
        • March L.M.
        • Roos E.M.
        • Nilsdotter A.K.
        • Brown G.C.
        • et al.
        Variation in age and physical status prior to total knee and hip replacement surgery: a comparison of centers in Australia and Europe.
        Arthritis Rheum. 2009; 61: 166-173
        • Gademan M.G.
        • Hofstede S.N.
        • Vliet Vlieland T.P.
        • Nelissen R.G.
        • Marang-van de Mheen P.J.
        Indication criteria for total hip or knee arthroplasty in osteoarthritis: a state-of-the-science overview.
        BMC Muscoskelet Disord. 2016; 17: 463
        • de Vet H.C.
        • Terwee C.B.
        The minimal detectable change should not replace the minimal important difference.
        J Clin Epidemiol. 2010; 63 (author reply 6): 804-805
        • Rouquette A.
        • Blanchin M.
        • Sebille V.
        • Guillemin F.
        • Cote S.M.
        • Falissard B.
        • et al.
        The minimal clinically important difference determined using item response theory models: an attempt to solve the issue of the association with baseline score.
        J Clin Epidemiol. 2014; 67: 433-440