Short Physical Performance Battery: What Does Each Sub-Test Measure in Patients with Chronic Obstructive Pulmonary Disease?

To identify phenotypic factors associated with the Short Physical Performance Battery (SPPB) and its individual sub-tests: standing balance, 4‑meter gait speed (4mGS) and 5-repetition sit-to-stand (5STS).The Evaluation of the Role of Inflammation in non-pulmonary disease manifestations in Chronic Airways disease (ERICA) study recruited adult participants with stable chronic obstructive pulmonary disease (COPD). Proportional odds models identified factors associated with the SPPB, and a principal component analysis (PCA) evaluated how much SPPB variance was explainable by each of its 3 sub-tests.Of 729 enrolled participants, 717 (60% male, mean age 67 years) had full SPPB data. Overall, 76% of patients had some evidence of functional limitations (SPPB total score < 12). Scores < 4 were observed in 71%, 31%, and 22% of participants for the 5STS, 4mGS, and balance sub-tests, respectively. A longer 6-minute walk test and greater quadriceps maximal voluntary contraction decreased the odds of being in a lower score category for SPPB total score and for all 3 sub-tests. Aging, self-reported hypertension and higher dyspnea increased the odds, and being married decreased the odds of being in a lower category for total score. All sub-tests contributed equally to total score.Each of the 3 sub-tests contributed independent information to the SPPB, demonstrating their usefulness for assessing COPD when considered together rather than individually. The 5STS sub-test had the greatest variation in scores and may thus have the best discriminatory power for clinical COPD studies of lower limb performance where only one SPPB test is feasible.