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Application of minimal important differences in degenerative knee disease outcomes: a systematic review and case study to inform BMJ Rapid Recommendations
  1. Tahira Devji1,
  2. Gordon H Guyatt1,2,
  3. Lyubov Lytvyn3,
  4. Romina Brignardello-Petersen1,4,
  5. Farid Foroutan1,5,
  6. Behnam Sadeghirad1,6,
  7. Rachelle Buchbinder7,8,
  8. Rudolf W Poolman9,
  9. Ian A Harris10,11,
  10. Alonso Carrasco-Labra1,4,
  11. Reed A C Siemieniuk1,12,
  12. Per O Vandvik13
  1. 1Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada
  2. 2Department of Medicine, McMaster University, Hamilton, Ontario, Canada
  3. 3Oslo University Hospital, Oslo, Norway
  4. 4Evidence-Based Dentistry, Faculty of Dentistry, Universidad de Chile, Santiago, Chile
  5. 5Heart Failure/Transplant Program, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
  6. 6HIV/STI Surveillance Research Center, and WHO Collaborating Center for HIV Surveillance, Institute for Futures Studies in Health, Kerman University of Medical Sciences, Kerman, Iran
  7. 7Department of Epidemiology and Preventive Medicine, School of Public Health & Preventive Medicine, Monash University, Melbourne, Australia
  8. 8Monash Department of Clinical Epidemiology, Cabrini Institute; Suite 41 Cabrini Medical Centre, Malvern, Victoria, Australia
  9. 9Department of Orthopaedic Surgery, Joint Research, OLVG, Amsterdam, The Netherlands
  10. 10South Western Sydney Clinical School, Sydney, New South Wales, Australia
  11. 11Whitlam Orthopaedic Research Centre, Level 2, Ingham Institute for Applied Medical Research, Liverpool, New South Wales, Australia
  12. 12Department of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada
  13. 13Department of Medicine, Innlandet Hospital Trust-Gjøvik, Gjøvik, Norway
  1. Correspondence to Dr Tahira Devji; devjits{at}


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
  • osteoarthritis
  • 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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