Test-retest, responsiveness, and minimal important change of the ability to perform physical activities of daily living questionnaire in individuals with type 2 diabetes and obesity

The Ability to Perform Physical Activities of Daily Living Questionnaire (APPADL) measures the self-reported ability of individuals with type 2 diabetes mellitus (T2DM) and obesity to perform daily physical activities. The primary objective of this study was to estimate APPADL test-retest reliability, responsiveness, and minimal important change (MIC). Study participants were individuals with T2DM and body mass index ≥30 kg/m(2) enrolled in clinical weight loss programs in the United States. Data were obtained for clinical measures, APPADL, and other patient-reported instruments. APPADL test-retest reliability was estimated with intraclass correlation coefficient. To estimate responsiveness in a subgroup of participants, baseline and 6-month data were analyzed using paired t test and calculation of responsiveness indices (e.g., effect size [ES]). To estimate MIC, both distribution-based and anchor-based methods were used. Test-retest data for 106 study participants (mean age, 52 years; 69% female; 31% white; mean body mass index, 38 kg/m(2)) yielded an intraclass correlation coefficient of 0.91. In the subgroup (n = 40) used to estimate responsiveness, weight was significantly less at end point than at baseline (mean, 222.0 vs. 231.9 pounds; P < 0.001, ES = 0.24), and APPADL scores were significantly better than at baseline (mean, 77.0 vs. 70.8; P = 0.01, ES = 0.32). Results of distribution- and anchor-based methods to establish MIC suggest values of 6-14 points (0-100 scale). The APPADL has demonstrated reliability and validity. In addition, it has demonstrated responsiveness to weight loss in individuals with T2DM and obesity, thereby making it a potentially valuable tool in the evaluation of weight loss interventions (e.g., antihyperglycemic medications that produce weight loss) targeted toward patients with T2DM.