Responsiveness of the late life disability instrument to pulmonary rehabilitation in people with COPD

PURPOSE: To establish the responsiveness of the disability component of the Late Life Function and Disability Instrument (LLDI) and its Computer Adaptive Test (LLDI-CAT) in people with chronic obstructive pulmonary disease (COPD). METHOD: Participants completed the LLDI, LLDI-CAT and measures of physical function, health-related quality of life (HRQOL) and symptom severity before and after pulmonary rehabilitation (PR), and global rating of change (GRC) scales at the end of PR. Responsiveness was explored by calculating correlations between LLDI and LLDI-CAT change scores and change scores on the other measures, and calculating the area under the receiver operating characteristic curve (AUC) for the ability of the LLDI and LLDI-CAT to discriminate between participants who were improved versus unchanged. We hypothesized fair correlations (-0.3 to -0.5 or 0.3 to 0.5) with other measures and considered an AUC≥0.7 acceptable. Minimal important differences (MIDs) were estimated using anchor- and distribution-based approaches. RESULTS: Fifty participants (mean (SD) age 69.8 (7.9) years) completed the study. Only the limitation dimension of the LLDI showed improvement at follow-up (z = 2.4, p = 0.018) and was able to discriminate between participants who were improved versus unchanged (AUC 0.7 (95% CI 0.6-0.9)). Correlations between change scores were as hypothesized between the participation measures and measures of at least two other constructs. CONCLUSION: This study provides MID values for the LLDI and LLDI-CAT to support their clinical application. The limitation dimension of the LLDI appears to be particularly responsive to PR in people with COPD.