Predictive Validity of the Short Physical Performance Battery for Frail States in Community-Dwelling Older Adults

INTRODUCTION

Frailty is prevalent in Singapore's rapidly ageing population. The Clinical Frailty Scale (CFS) is a widely adopted frailty assessment tool chosen for its ease of use and predictive accuracy. However, CFS grading requires clinical judgment, introducing subjectivity and potential inter-rater variability. The Short Physical Performance Battery (SPPB) is an objective measure of physical function that can predict disability and mortality in older adults, with declining scores suggesting increased frailty. This study aimed to determine the correlation of SPPB to CFS in identifying frail states among community-dwelling older adults.

METHODS

CFS scores were determined by an independent assessor, and individuals were classified into non-frail (CFS 1-3), pre-frail (CFS 4), and frail (CFS 5-6) groups. SPPB scores were measured for all participants. Receiver operating characteristic (ROC) analyses were performed to evaluate the discriminative ability of SPPB for frail states.

RESULTS

The sample included 95 non-frail, 34 pre-frail, and 30 frail individuals (mean ages 76, 77, and 80 years respectively). Median SPPB scores were 11, 10, and 9.5 for non-frail, pre-frail, and frail groups respectively. For pre-frailty, an SPPB cutoff of ≤10 achieved an AUC of 0.72 (95% CI: 0.63-0.82), with 79% sensitivity and 67% specificity. For frailty, an SPPB cutoff of ≤8 resulted in an AUC of 0.69 (95% CI: 0.59-0.80), with 37% sensitivity and 90% specificity.

CONCLUSIONS

SPPB scores correlate well with CFS-defined frailty states despite fundamental differences in assessment approaches. While SPPB showed acceptable diagnostic performance overall, its low sensitivity for frailty suggests it may miss individuals whose deficits are primarily non-physical. However, SPPB's objectivity and reproducibility makes it a reliable alternative for community-based frailty screening, particularly where inter-rater variability is a concern. Our findings support using SPPB as a practical screening tool to identify those who may benefit from early intervention.