Reliable change and minimum important difference (MID) proportions facilitated group responsiveness comparisons using individual threshold criteria
Schmitt, John S.; Di Fabio, Richard P.
Journal of Clinical Epidemiology
OBJECTIVE: This study contrasted the use of responsiveness indices at the group level vs. individual patient level. STUDY DESIGN AND SETTING: We followed a cohort of 211 patients (50% male; mean age 47.5 years; SD 14) with musculoskeletal upper extremity problems for a total of 3 months. Outcome measures included the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, Shoulder Pain and Disability Index (SPADI), Patient-Rated Wrist Evaluation (PRWE), and the Medical Outcomes Study 12-Item Short-Form Health Survey (SF-12). We calculated confidence intervals on various group-level responsiveness statistics based on effect size and correlation with global change. The proportion of patients exceeding the minimum detectable change (or reliable change proportion) and minimum important difference (MID proportion) were included as indices applicable to the individual patient. RESULTS: For the DASH, effect size ranged from 1.06 to 1.67 for various patient subgroups, and the reliable change and MID proportions indicated that 50%-70% of individuals exhibited change based on individual change scores. Only the SRM and reliable change proportion indicated differences among the outcome measures used in this study. CONCLUSION: The reliable change and MID proportions have an intuitive interpretation and facilitate quantitative responsiveness comparisons among outcome measures based on individual patient criteria.