The Short Physical Performance Battery is a discriminative tool for identifying patients with COPD at risk of disability

Background: Limited mobility is a risk factor for developing chronic obstructive pulmonary disease (COPD)-related disabilities. Little is known about the validity of the Short Physical Performance Battery (SPPB) for identifying mobility limitations in patients with COPD. Objective: To determine the clinical validity of the SPPB summary score and its three components (standing balance, 4-meter gait speed, and five-repetition sit-to-stand) for identifying mobility limitations in patients with COPD. Methods: This cross-sectional study included 137 patients with COPD, recruited from a hospital in Spain. Muscle strength tests and SPPB were measured; then, patients were surveyed for self-reported mobility limitations. The validity of SPPB scores was analyzed by developing receiver operating characteristic curves to analyze the sensitivity and specificity for identifying patients with mobility limitations; by examining group differences in SPPB scores across categories of mobility activities; and by correlating SPPB scores to strength tests. Results: Only the SPPB summary score and the five-repetition sit-to-stand components showed good discriminative capabilities; both showed areas under the receiver operating characteristic curves greater than 0.7. Patients with limitations had significantly lower SPPB scores than patients without limitations in nine different mobility activities. SPPB scores were moderately correlated with the quadriceps test (r>0.40), and less correlated with the handgrip test (r<0.30), which reinforced convergent and divergent validities. A SPPB summary score cutoff of 10 provided the best accuracy for identifying mobility limitations. Conclusion: This study provided evidence for the validity of the SPPB summary score and the five-repetition sit-to-stand test for assessing mobility in patients with COPD. These tests also showed potential as a screening test for identifying patients with COPD that have mobility limitations.