Diagnostic accuracy of the Fast Timed Up and Go test for identifying low lower-limb functional power in community-dwelling Thai older women: a cross-sectional study using sit-to-stand-derived muscle power as the reference standard.

Abstract

Background: The Fast Timed Up and Go (FTUG) test is a simple mobility assessment that may serve as a practical alternative for identifying low lower-limb functional power in community settings. This study aimed to evaluate the diagnostic accuracy of FTUG for detecting low functional power and to determine an optimal population-specific cutoff in community-dwelling older Thai women.

Methods: A cross-sectional diagnostic accuracy study was conducted among 88 community-dwelling women aged ≥60 years. Relative sit-to-stand (STS) muscle power was calculated using the Alcazar equation, and low power was defined as a value below the 25th percentile of the sample distribution (2.36 W/kg). Diagnostic accuracy of FTUG was evaluated using receiver operating characteristic (ROC) analysis, with the optimal cutoff identified using the Youden index.

Results: Participants with low STS-derived power demonstrated significantly slower FTUG times than those with normal power (12.43±3.72 seconds vs. 8.33±1.08 seconds, P<0.001). ROC analysis showed strong discriminatory capacity, with an area under the ROC curve of 0.922 (95% confidence interval, 0.855-0.989). The optimal FTUG cutoff was 9.8 seconds, yielding 77.3% sensitivity and 93.9% specificity. Alternative thresholds showed acceptable performance but did not exceed the overall accuracy of the 9.8-second cutoff.

Conclusion: FTUG demonstrated high diagnostic accuracy for identifying reduced lower-limb functional power in community-dwelling older Thai women. A population-specific cutoff of 9.8 seconds may provide a practical tool for early screening in community health settings.