REPRODUCIBILITY OF EUCAPNIC VOLUNTARY HYPERVENTILATION FOR EXERCISE-INDUCED BRONCHOSPASM DIAGNOSIS IN ASTHMATIC CHILDREN AND ADOLESCENTS.

BACKGROUND: Exercise-induced respiratory symptoms are frequently reported by asthmatics and exercise-induced bronchospasm (EIB) is a frequent cause that requires objective testing for diagnosis. Eucapnic voluntary hyperventilation (EVH) is recommended as an exercise surrogate stimulus for this purpose, but its short-term reproducibility is not yet established in young asthmatics. OBJECTIVE: To evaluate the short-term test-retest agreement and reproducibility of FEV1 changes after EVH in young asthmatics. METHODS: Asthmatics aged between 10 and 20 years underwent EVH for EIB diagnosis on two occasions 2-4 days apart at a specialized university clinic. FEV1 was measured 5, 15 and 30 minutes after EVH with a target ventilation rate 21 times baseline FEV1. EIB was diagnosed as a decrease >10% in FEV1 from baseline. RESULTS: Twenty-six of 62 recruited individuals tested positive for EIB on both visits (positive group) and 17 on one visit only (divergent group); and 19 tested negative on both visits (negative group). The overall agreement was 72.5% (95%CI 61.6%, 83.6%) and positive and negative agreement was 41.9% and 30.6% respectively. Despite overall low bias in FEV1 response between test days (0.87%), the limits of agreement were wide (+20.72%). There were no differences in pre-challenge FEV1 or achieved ventilation rate, between visits either between groups (p=0.097 and p=0.461) or within groups, (p=0.828 and p=0.780). No test was interrupted by symptoms and there were no safety issues. CONCLUSIONS: More than one EVH test should be performed in young asthmatics with a negative test to exclude EIB and minimize misdiagnosis and mistreatment.