Reproducibility of peak oxygen uptake and other cardiopulmonary exercise parameters: Implications for clinical trials and clinical practice

Background: Clinical trialists involved in projects aimed at assessing the impact of a device or therapy on exercise capacity must select an end point that can detect a therapy-derived change and do so in a manner that is both sensitive to the change and valid. Using baseline data from the Prospective Evaluation of Elastic Restraint to Lessen the Effects of Heart Failure (PEERLESS-HF) trial, we describe the coefficient of variation (CV) for peak oxygen uptake (V̇O₂) and other parameters measured during a cardiopulmonary exercise (CPX) test. Methods: Prior to conducting CPX testing, a CPX core laboratory conducted training with testing staff at each site, and a standardized quality assurance protocol was completed. During screening, subjects performed two symptom-limited CPX tests (CPX-0 and CPX-1) within 14 days. Results: The CVs for peak V̇O₂, ventilatory efficiency, and ventilatory-derived anaerobic threshold were 5.9%, 4.8%, and 6.8%, respectively. During CPX-0, the percentage of subjects with a respiratory exchange ratio (RER) < 1.05 who increased their peak V̇O₂ by ≥ 6% during CPX-1 was 47%, compared with 12% of subjects also with an RER < 1.05 who experienced a decrease in peak V̇O₂ ≥ 6%. Conclusions: In a multisite clinical trial setting, we showed that the achieved test-retest reproducibility for peak V̇O₂ can be acceptable, as evidenced by a CV at 5.9%. Until more data are available to identify patients who may demonstrate greater test-retest variance and to avoid repeat testing in all subjects at baseline, clinical trialists might consider repeating tests when RER < 1.05. Trial registration: clinicaltrials.gov; Identifier: NCT00382863.