The accuracy with which the 5 times sit-to-stand test, versus gait speed, can identify poor exercise tolerance in patients with COPD
Identifying those patients who underperform in the 6-minute walk test (6MWT <350 m), and the reasons for their poor performance, is a major concern in the management of chronic obstructive pulmonary disease.To explore the accuracy and relevance of the 4-m gait-speed (4MGS) test, and the 5-repetition sit-to-stand (5STS) test, as diagnostic markers, and clinical determinants, of poor performance in the 6MWT.We recruited 137 patients with stable chronic obstructive pulmonary disease to participate in our cross-sectional study. Patients completed the 4MGS and 5STS tests, with quantitative (in seconds) and qualitative ordinal data collected; the latter were categorized using a scale of 0 to 4. The following potential covariates and clinical determinants of poor 6MWT were collated: age, quadriceps muscle-strength (QMS), health status, dyspnea, depression, and airflow limitation. Area under the receiver-operating characteristic curve data (AUC) was used to assess accuracy, with logistic regression used to explore relevance as clinical determinants.The AUCs generated using the 4MGS and 5STS tests were comparable, at 0.719 (95% confidence interval [CI] 0.629-0.809) and 0.711 (95% CI 0.613-0.809), respectively. With ordinal data, the 5STS test was most accurate (AUC of 0.732; 95% CI 0.645-0.819); the 4MGS test showed poor discriminatory power (AUC <0.7), although accuracy improved (0.726, 95% CI 0.637-0.816) when covariates were included. Unlike the 4MGS test, the 5STS test provided a significant clinical determinant of a poor 6MWT (odds ratio 1.23, 95% CI 1.05-1.44).The 5STS test reliably predicts a poor 6MWT, especially when using ordinal data. Used alone, the 4MGS test is reliable when measured with continuous data.