Defining Clinically Meaningful Cut Points for Leg Power Impairment Using Physical Performance in Older Adults: A Secondary Analysis From Boston RISE

Abstract

Objective: To identify clinically meaningful thresholds of leg power impairment identified by the stair climb power test (SCPT).

Design: Cross-sectional analysis using the baseline data from an observational cohort study.

Setting: The Boston Rehabilitative Impairment Study of the Elderly.

Participants: Community-dwelling older adults (N=413).

Main outcome measures: SCPT and the Short Physical Performance Battery (SPPB).

Results: Using the receiver operating characteristic curves and Youden's J statistics, the optimal threshold for the SCPT associated with mobility limitation as defined by an SPPB score ≤9 was 3.07 Watts/kg for men with a sensitivity of 74%, a specificity of 73% and, an area under the curve (AUC) value of 0.78. For women, the optimal threshold was 2.59 Watts/kg with a sensitivity of 83%, a specificity of 69%, and an AUC value of 0.81. The classification and regression tree sensitivity analysis demonstrated similar thresholds, 2.88 Watts/kg and 2.53 Watts/kg for men and women, respectively.

Conclusions: The study identified clinically meaningful thresholds of impairment for the SCPT for mobility limited older primary care patients. These thresholds may be used to inform rehabilitation care to improve functional mobility of older adults and should be validated in larger more representative clinical trials.

Keywords: Mobility limitation; Rehabilitation; Short physical performance battery; Stair climb power test.