Background: Minimal important difference (MID) has been defined as “the smallest difference (in score) that patients perceive as important, and which would lead the clinician to consider a change in the patient’s management’’. Due to the importance of this concept for decision-making, more studies have emerged to provide evidence of MIDs for several patient-reported outcomes. One specific MID tool was recently developed to evaluate the quality of this type of study, however, there are still some gaps related to the application of this instrument.
Objectives: To report challenges when applying a tool developed to analyze the credibility of studies that report MIDs according to the anchor-based methods.
Methods: This secondary analysis of a systematic review synthesized MIDs for outcomes related to urinary incontinence (UI) measures. The credibility of each MID reported (according to anchor-based methods) was determined by two independent assessors. The MID tool was used under license authorization from McMaster University.
Results: Sixty-five different MIDs were assessed by the MID tool. We identified a high level of subjectivity when assessing the MIDs' credibility by each domain, which led to conflicts between authors. There was no specific guidance on how to summarize different domains of this tool to report a final assessment of credibility for each MID. Decision rules to determine a final score of credibility of the MIDs were established by the authors of this review and were based on similar decision rules done in the context of RoB assessment of RCTs. Further validation of this tool is necessary.
Conclusions: There are still some gaps related to the application of the MID tool. Future studies should move forward on this topic to improve the domains assessed by the tool and further validation of this instrument should be performed. The development of a tool to assess the credibility of the MIDs according to the distribution-based methods is required.
Patient, public and/or healthcare consumer involvement: The development of better rules and tools for assessing the credibility of the MIDs benefits the patients since the effectiveness of treatments will be better evaluated, and consequently the results obtained will be more accurate.