Comparison of the responsiveness of the FIM and the interRAI post acute care assessment instrument in rehabilitation of older adults

OBJECTIVE: To compare the responsiveness of 2 major systems developed for rehabilitation settings--the FIM and the interRAI Post Acute Care (PAC) assessment--in older patients. DESIGN: Trained raters assessed patients with both tools at admission and discharge. SETTING: Musculoskeletal (MSK) and geriatric rehabilitation units (GRUs) in 2 rehabilitation hospitals. PARTICIPANTS: Older adults receiving rehabilitation (N=208; mean age +/- SD, 78.5+/-9.3; 67% women). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Responsiveness was evaluated using effect size (ES) and standardized response mean (SRM). RESULTS: ES and SRM were somewhat higher for the FIM motor (GRU ES=1.68, SRM=1.31; MSK ES=2.12, SRM=2.25) than the PAC (GRU ES=1.64, SRM=1.29; MSK ES=1.57, SRM=1.89) in both patient groups. Both tools were more responsive in MSKs than GRUs. This may reflect the greater frailty and clinical complexity of GRU patients. CONCLUSIONS: Both the FIM motor and the PAC were able to detect clinically relevant improvement in functional ability in older rehabilitation inpatients.