Objectives To identify the most credible anchor-based minimal important differences (MIDs) for patient important outcomes in patients with degenerative knee disease, and to inform BMJ Rapid Recommendations for arthroscopic surgery versus conservative management
Design Systematic review.
Outcome measures Estimates of anchor-based MIDs, and their credibility, for knee symptoms and health-related quality of life (HRQoL).
Data sources MEDLINE, EMBASE and PsycINFO.
Eligibility criteria We included original studies documenting the development of anchor-based MIDs for patient-reported outcomes (PROs) reported in randomised controlled trials included in the linked systematic review and meta-analysis and judged by the parallel BMJ Rapid Recommendations panel as critically important for informing their recommendation: measures of pain, function and HRQoL.
Results 13 studies reported 95 empirically estimated anchor-based MIDs for 8 PRO instruments and/or their subdomains that measure knee pain, function or HRQoL. All studies used a transition rating (global rating of change) as the anchor to ascertain the MID. Among PROs with more than 1 estimated MID, we found wide variation in MID values. Many studies suffered from serious methodological limitations. We identified the following most credible MIDs: Western Ontario and McMaster University Osteoarthritis Index (WOMAC; pain: 12, function: 13), Knee injury and Osteoarthritis Outcome Score (KOOS; pain: 12, activities of daily living: 8) and EuroQol five dimensions Questionnaire (EQ-5D; 0.15).
Conclusions We were able to distinguish between more and less credible MID estimates and provide best estimates for key instruments that informed evidence presentation in the associated systematic review and judgements made by the Rapid Recommendation panel.
Trial registration number CRD42016047912.
- Minimal Important difference
- Minimal clinically important difference
- patient reported outcomes
- degenerative knee disease
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Contributors TD, GHG, AC-L, RACS and POV conceived the study idea. TD and AC-L performed the literature search. AC-L and GHG, among other colleagues, developed the credibility tool (core criteria) used in this study. TD performed the data analysis. TD, GHG, RWP, RB and RACS interpreted the data analysis. TD and GHG wrote the first draft of the manuscript. TD, LL, BS and FF acquired the data and performed credibility assessments. TD, GHG, POV, RWP and RB-P critically revised the manuscript. TD had full access to all of the data in the study, and takes responsibility for the integrity of the data and the accuracy of the data analysis. TD is the guarantor.
Funding TD, ACL, and GHG are Canadian Institutes of Health Research, Knowledge Synthesis grant recipients for projects related to MID methods (ACL and GHG grant # DC0190SR; TD, ACL, and GHG grant # DC0190SR). RB-P is funded by an Australian National Health and Medical Research Council (NHMRC) Senior Principal Research Fellowship.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional data are available.
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