Test-retest repeatability of cardiopulmonary exercise test variables in patients with cardiac or respiratory disease

Background The test-retest reliability for multiple cardiopulmonary exercise test (CPX) variables has not been compared in a single study and the influence of different diseases on test-retest reliability has not been examined. We investigated different measures of test-retest reliability for multiple variables and compared them by category of cardiac or respiratory disease. Methods Patients with chronic obstructive airways disease (n = 24), heart failure (n = 43), or severe mitral valve disease (n = 26) were recruited into a prospective study. Each patient underwent two bicycle ergometer tests; the first, a familiarization test, with a 10 W/min ramp, and the second a personalized ramp based on the results of the familiarization test to elicit maximal effort within 8-10 min. Intraclass correlation coefficients (ICC) and coefficients of variation between the two tests were calculated. Influence of potential modifiers was assessed using repeated measures analysis of variance. Results Peak VO2 (ICC 0.95, 95% CI 0.94-0.97), oxygen uptake efficiency slope (ICC 0.93, 95% CI 0.90-0.95), O-2 pulse (ICC 0.96, 95% CI 0.94-0.97), and the VE/VCO2 ratio at the nadir (ICC 0.92, 95% CI 0.89-0.95) all showed excellent test-retest reliability, with within-subject coefficients of variation <0.12. VO2 at the anaerobic threshold (ICC 0.84, 95% CI 0.78-0.89) and the VE/VCO2 slope (ICC 0.88, 95% CI 0.79-0.93) showed good test-retest reliability, although inferior to peak VO2. Age, gender, body mass index, disease aetiology, protocol change, and intertest interval did not affect the reliability of most variables. Conclusions CPX showed high test-retest reliability; certain variables such as peak VO2 and oxygen uptake efficiency slope outperform others. These results identify which variables are most suitable for serial testing of patients with three common disease aetiologies owing to their superior reproducibility.