A Standard Method for Determining the Minimal Clinically Important Difference for Rehabilitation Measures.

The minimal clinically important difference (MCID) is receiving increasing interest and importance in medical practice and research. The MCID is the smallest improvement in scores in the domain of interest that patients perceive as beneficial. In clinical trials, comparing the proportion of individuals between treatment and control groups who obtain a MCID may be more informative than comparisons of mean change between groups because a statistically significant mean difference does not necessarily represent a difference that is perceived as meaningful by treatment recipients. The MCID may also be useful in advancing personalized medicine by characterizing those who are most likely to benefit from a treatment. In clinical practice, the MCID can be used to identify if a participant is experiencing a meaningful change in status. A variety of methods have been used to determine the MCID with no clear agreement on the most appropriate approach. Two major sets of methods are either (1) distribution-based, that is, referencing the MCID to a measure of variability or effect size in the measure of interest or (2) anchor-based, that is, referencing the MCID to an external assessment of change in the condition, ability, or activity represented by the measure of interest. In prior literature, using multiple methods to "triangulate" on the value of the MCID has been proposed. In this commentary, we describe a systematic approach to triangulate on the MCID using both distribution-based and anchor-based methods. Adaptation of a systematic approach for obtaining the MCID in rehabilitation would facilitate communication and comparison of results among rehabilitation researchers and providers.