How consistent is the determination of the anaerobic threshold among members of the same cardiac rehabilitation team?

Introduction: Consistency in the anaerobic threshold (AT) determination is essential for cardiac rehabilitation teams comprising multiple professionals who conduct cardiopulmonary exercise tests (CPETs) and interpret their results. The effect of years of experience on interpreting CPET results, including the AT, has been examined. However, consistency in the AT determination among members of the same institution with experience beyond the training period has not been reported. Methods: We evaluated consistency in the AT determination among four members at a cardiovascular hospital (three full-time physical therapists and one part-time consultant physician) with 4 to 30 years of experience with CPETs. Another full-time physical therapist acted as the controller and did not participate in the AT reading. This retrospective study used 260 blinded and randomized CPET data files from 130 patients (130 data pairs comprising inpatient and outpatient data). All observers determined the AT twice using the modified V-slope method. Results: The mean AT values showed significant interobserver differences (p<0.001) driven by a slightly but significantly lower value determined by the consultant physician. No significant differences in the values determined by the three full-time staff members were observed. Despite interobserver differences during inpatient and outpatient phases, the longitudinal change in the AT did not differ significantly (p=0.58). The intrarater reliability of four observers was good [intraclass correlation coefficient (1,1) = 0.87-0.94], with limits of agreement of 103.6 to 185.0 mL/min. The inter-rater reliability was also good [intraclass coefficient (2,1) = 0.87], with limits of agreement of observer pairs of 139.2 to 220.5 mL/min. Reliability was not associated with years of experience. Conclusions: Good consistency in the AT determination is achievable in a clinical setting. Adherence to a single standardized method across the team likely facilitates this consistency and provides a reliable objective measure for monitoring exercise tolerance.