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Evaluating the credibility of anchor based estimates of minimal important differences for patient reported outcomes: instrument development and reliability study.

  • Devji, Tahira1
  • Carrasco-Labra, Alonso2
  • Qasim, Anila2
  • Phillips, Mark2
  • Johnston, Bradley C2, 3
  • Devasenapathy, Niveditha4
  • Zeraatkar, Dena2
  • Bhatt, Meha2
  • Jin, Xuejing5
  • Brignardello-Petersen, Romina2
  • Urquhart, Olivia6
  • Foroutan, Farid2
  • Schandelmaier, Stefan2
  • Pardo-Hernandez, Hector7, 8
  • Vernooij, Robin Wm9
  • Huang, Hsiaomin10
  • Rizwan, Yamna11
  • Siemieniuk, Reed2
  • Lytvyn, Lyubov2
  • Patrick, Donald L12
  • And 7 more
  • 1 Department of Health Research Methods, Evidence and Impact, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada [email protected] , (Canada)
  • 2 Department of Health Research Methods, Evidence and Impact, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada. , (Canada)
  • 3 Department of Community Health and Epidemiology, Dalhousie University, Halifax, NS, Canada. , (Canada)
  • 4 Indian Institute of Public Health, Public Health Foundation of India, Gujarat, India. , (India)
  • 5 School of Public Health, University of Alberta, Edmonton, AB, Canada. , (Canada)
  • 6 Center for Evidence Based Dentistry, American Dental Association, Chicago, IL, USA.
  • 7 Iberoamerican Cochrane Centre, Sant Pau Biomedical Research Institute (IIB Sant Pau), Barcelona, Spain. , (Spain)
  • 8 CIBER de Epidemiología y Salud Pública (CIBERESP), Barcelona, Spain. , (Spain)
  • 9 Department of Research, Comprehensive Cancer Organisation, Utrecht, Netherlands. , (Netherlands)
  • 10 Department of Orthopedic Surgery, University of Michigan, Ann Arbor, MI, USA.
  • 11 Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada. , (Canada)
  • 12 Department of Health Services, University of Washington, Seattle, WA, USA.
  • 13 Department of Health Promotion and Human Behaviour, School of Public Health, Kyoto University Graduate School of Medicine, Kyoto, Japan. , (Japan)
  • 14 Nephrology Program, Humber River Regional Hospital, Toronto, ON, Canada. , (Canada)
  • 15 Division of Nephrology, University of Western Ontario, London, ON, Canada. , (Canada)
  • 16 Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, ON, Canada. , (Canada)
  • 17 Department of Medicine, McMaster University, Hamilton, ON, Canada. , (Canada)
  • 18 Department of Surgery, McMaster University, Hamilton, ON, Canada. , (Canada)
Published Article
Publication Date
Jun 04, 2020
DOI: 10.1136/bmj.m1714
PMID: 32499297


To develop an instrument to evaluate the credibility of anchor based minimal important differences (MIDs) for outcome measures reported by patients, and to assess the reliability of the instrument. Instrument development and reliability study. Initial criteria were developed for evaluating the credibility of anchor based MIDs based on a literature review (Medline, Embase, CINAHL, and PsycInfo databases) and the experience of the authors in the methodology for estimation of MIDs. Iterative discussions by the team and pilot testing with experts and potential users facilitated the development of the final instrument. With the newly developed instrument, pairs of masters, doctoral, or postdoctoral students with a background in health research methodology independently evaluated the credibility of a sample of MID estimates. Core credibility criteria applicable to all anchor types, additional criteria for transition rating anchors, and inter-rater reliability coefficients were determined. The credibility instrument has five core criteria: the anchor is rated by the patient; the anchor is interpretable and relevant to the patient; the MID estimate is precise; the correlation between the anchor and the outcome measure reported by the patient is satisfactory; and the authors select a threshold on the anchor that reflects a small but important difference. The additional criteria for transition rating anchors are: the time elapsed between baseline and follow-up measurement for estimation of the MID is optimal; and the correlations of the transition rating with the baseline, follow-up, and change score in the patient reported outcome measures are satisfactory. Inter-rater reliability coefficients (ĸ) for the core criteria and for one item from the additional criteria ranged from 0.70 to 0.94. Reporting issues prevented the evaluation of the reliability of the three other additional criteria for the transition rating anchors. Researchers, clinicians, and healthcare policy decision makers can consider using this instrument to evaluate the design, conduct, and analysis of studies estimating anchor based minimal important differences. © Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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