Evaluating and understanding performance testing in COPD patients.

Purpose. There is increasing interest in the use of performance tests to assess physical function among patients with debilitating diseases. The purpose of this study was to describe the measurement properties of a performance test battery used in the Reconditioning Exercise and Chronic Obstructive Pulmonary Disease Trial and to explore how well-selected physiologic and psychosocial measures explained test performance. Methods. To assess test-retest reliability of the performance tests, older patients with chronic obstructive pulmonary disease (n = 30) completed, on two different occasions, a 6-minute walk for distance, a timed stair climb, and a timed elevated-arm task. In addition, stepwise regression analyses were conducted on a larger sample (n = 209) to examine how effective conceptually relevant physiologic and psychosocial variables were at explaining variation in task performance. Results. Results showed that all three performance tasks had good test-retest reliability (all coefficients > 0.80) and shared variance in expected directions with VO2peak, forced expiratory volume in 1 second (FEV1), and self-reported disability. Regression analyses suggest that VO2peak, FEV1, self-efficacy, and self-reported disability are important variables to consider in attempts to understand performance-related disability in patients with chronic obstructive pulmonary disease (COPD). Conclusions. The physical performance test battery appears to be a reliable means of assessing physical functioning in older patients with COPD. Furthermore, findings support the important role that VO2peak plays in task performance and suggest that patients' perceptions should be given careful consideration when attempting to understand physical decline in clinical settings.