Test-retest reliability of cardiopulmonary exercise test-derived metrics in individuals with COPD versus healthy controls

BACKGROUND: Cardiopulmonary exercise testing (CPET) is usually considered the gold standard for assessing maximal oxygen consumption (V̇O2max), a health and performance marker in patients with chronic obstructive pulmonary disease (COPD). Despite the widespread application of CPET, the absolute and relative test-retest reliability of CPET-derived metrics remains unexamined.

OBJECTIVE: To examine and compare test-retest reliability of CPET derived metrics in individuals with COPD and healthy matched controls.

METHODS: 12 individuals with COPD and 12 healthy age- and sex-matched controls were included in this case-control study. Each participant completed two CPET on a bicycle ergometer on two different days. Absolute reliability was reported as smallest real difference (SRD) and relative reliability as coefficient of variance (CV) and intraclass correlation coefficients (ICC).

MAIN RESULTS: SRD for peak oxygen uptake was 451.6 (267.4;1006.4) mL/min and CV was 7.8 (4.7;11.0)% in patients with COPD, whereas SRD was 244.2 (151.4;491.5) mL/min and CV was 3.0 (1.8;4.2)% in healthy controls but with no significant between group difference for SRD. CV values for all CPET derived metrics were found to be below 10%. Apart from peak workload achieved and peak minute ventilation, SRD and CV were significantly higher in COPD than in controls for all other CPET-derived metrics.

CONCLUSION: This study provides test-retest reliability estimates of the most widely used CPET derived metrics in individuals with COPD and healthy matched controls. Test-retest reliability for most metrics derived from CPET were found to be lower in individuals with COPD when compared to healthy controls.