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

Abstract

Objective 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. Design Instrument development and reliability study. Data sources 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. Participants 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. Main outcome measures Core credibility criteria applicable to all anchor types, additional criteria for transition rating anchors, and inter-rater reliability coefficients were determined. Results 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. Conclusions 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.

Minimal important difference and patient acceptable symptom state for pain, Constant-Murley score and Simple Shoulder Test in patients with subacromial pain syndrome

“…Given the relatively long interval between the baseline and first follow-up, risk of recall bias is obvious. This notion is supported by very low correlations between the transition item and baseline and lower correlations to change scores than to the post scores [ 21 , 22 ]. This is an inherent weakness of the GRC in a setting where the condition needs longer to evolve than a reliable recall time frame [ 22 ].…”

“…An adequate transition anchor should correlate to the change in outcome, and ideally correlate equally, but in opposite directions to the scores of outcomes at baseline and at follow-up time points (post scores) [ 21 ]. The correlation to change should be larger than the correlation to post scores when the GRC captures true change [ 22 ]. To explore this, we calculated the correlation coefficients (Spearman’s rho) for the GRC answers at different time points and baseline scores, the GRC and each of the respective post scores and the post scores of the combined dataset, and the GRC and the change scores of the outcomes, also at follow-up time points and the combined dataset.…”

Functional Outcomes of Arthroscopic Partial Meniscectomy Versus Physical Therapy for Degenerative Meniscal Tears Using a Patient-Specific Score: A Randomized Controlled Trial

“…Before statistical analyses, we calculated the minimal important change (MIC) of the PSFS in our population, using an anchor-based method, to provide a context of clinical relevance. 7 The anchor question was the following: “How did your function in daily activities change since the surgery/treatment of your knee?” A detailed description of the methods and results for the MIC calculation can be found in Appendix 2.…”

Conservative treatment of partial-thickness rotator cuff tears and tendinopathy with platelet-rich plasma: a systematic review and meta-analysis

“…According to previous studies the values of MCID were reported as 1.0 (VAS), 26 5.5(CMS), 14.88 (SPADI), and 11.1 (ASES), 27, 28 respectively. In this study, the minimal important differences (MIDs) between two groups calculated by anchor-based methods 29 were compared with those MCIDs. Therefore, clinical improvements were deemed meaningful when the MIDs calculated were beyond MCIDs.…”