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Minimally important difference estimates and methods: a protocol
  1. Bradley C Johnston1,2,3,4,
  2. Shanil Ebrahim1,4,5,6,7,
  3. Alonso Carrasco-Labra4,8,
  4. Toshi A Furukawa9,
  5. Donald L Patrick10,
  6. Mark W Crawford1,
  7. Brenda R Hemmelgarn11,
  8. Holger J Schunemann4,12,
  9. Gordon H Guyatt4,12,
  10. Gihad Nesrallah13,14,15
  1. 1Department of Anaesthesia and Pain Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
  2. 2Child Health Evaluative Sciences, The Research Institute, The Hospital For Sick Children, Hospital for Sick Children, Toronto, Ontario, Canada
  3. 3Institute of Health Policy, Management and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
  4. 4Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada
  5. 5Department of Anesthesia, McMaster University, Hamilton, Ontario, Canada
  6. 6Department of Medicine, Stanford Prevention Research Center, Stanford University, Stanford, California, USA
  7. 7Meta-Research Innovation Center at Stanford (METRICS), Stanford University, Stanford, California, USA
  8. 8Evidence-Based Dentistry Unit, Faculty of Dentistry, Universidad de Chile, Independencia, Santiago, Chile
  9. 9Department of Health Promotion and Human Behavior, School of Public Health, Kyoto University Graduate School of Medicine, Kyoto, Japan
  10. 10Department of Health Services, University of Washington, Seattle, Washington, USA
  11. 11Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada
  12. 12Department of Medicine, McMaster University, Hamilton, Ontario, Canada
  13. 13Nephrology Program, Humber River Regional Hospital, Toronto, Ontario, Canada
  14. 14Division of Nephrology, University of Western Ontario, London, Ontario, Canada
  15. 15Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
  1. Correspondence to Dr Gihad Nesrallah; gnesrallah{at}


Introduction Patient-reported outcomes (PROs) are often the outcomes of greatest importance to patients. The minimally important difference (MID) provides a measure of the smallest change in the PRO that patients perceive as important. An anchor-based approach is the most appropriate method for MID determination. No study or database currently exists that provides all anchor-based MIDs associated with PRO instruments; nor are there any accepted standards for appraising the credibility of MID estimates. Our objectives are to complete a systematic survey of the literature to collect and characterise published anchor-based MIDs associated with PRO instruments used in evaluating the effects of interventions on chronic medical and psychiatric conditions and to assess their credibility.

Methods and analysis We will search MEDLINE, EMBASE and PsycINFO (1989 to present) to identify studies addressing methods to estimate anchor-based MIDs of target PRO instruments or reporting empirical ascertainment of anchor-based MIDs. Teams of two reviewers will screen titles and abstracts, review full texts of citations, and extract relevant data. On the basis of findings from studies addressing methods to estimate anchor-based MIDs, we will summarise the available methods and develop an instrument addressing the credibility of empirically ascertained MIDs. We will evaluate the credibility of all studies reporting on the empirical ascertainment of anchor-based MIDs using the credibility instrument, and assess the instrument's inter-rater reliability. We will separately present reports for adult and paediatric populations.

Ethics and dissemination No research ethics approval was required as we will be using aggregate data from published studies. Our work will summarise anchor-based methods available to establish MIDs, provide an instrument to assess the credibility of available MIDs, determine the reliability of that instrument, and provide a comprehensive compendium of published anchor-based MIDs associated with PRO instruments which will help improve the interpretability of outcome effects in systematic reviews and practice guidelines.

  • MID
  • Minimally Important Difference
  • Patient Reported Outcome
  • Systematic Survey
  • Protocol

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