Allergen bronchoprovocation: Correlation between FEV1 maximal percent fall and area under the FEV1 curve and impact of allergen on recovery.

Abstract

Abstract Background House dust mite (HDM) induces greater responses than other allergens during allergen bronchoprovocation (ABP) testing. The two standardized methods for reporting results of ABP tests are the maximal percent fall in forced expiratory volume in one second (FEV1, max; %) and the area under the FEV1 vs time curve (AUC; %FEV1 x min). The relationship between these two methods has not been previously investigated. Aims Our first objective was to measure the correlation between FEV1, max and AUC during the early asthmatic response (EAR) and the late asthmatic response (LAR). Second, we aimed to determine if the EAR recovery period for HDM would be longer than other allergens (cat, grass, horse, and ragweed). Methods We retrospectively calculated EAR(0−2h) and LAR(3−7h) AUC and examined correlation between FEV1, max and AUC for both EAR(0−2h) and LAR(3−7h) for each listed allergen. We compared EAR(0−3h) and LAR(3−7h) FEV1, max, AUC and absolute difference in FEV1, max to the most recovered FEV1 (FEV1, min) 3 hours post-challenge for each allergen (third hour included to measure the EAR ending). We performed pairwise comparisons of correlation and slope values using Fischer’s r to z transformation and t-tests, respectively. AUC and absolute differences in FEV1, max and FEV1, min were compared using a one-way ANOVA test, followed by a post-hoc Scheffe test. Results Correlation between the EAR(0−2h) FEV1, max and the AUC (n = 221) was 0.807, and for the LAR(3−7h) (n = 157 of 221) was 0.798, (difference p = 0.408). The EAR(0−3h) AUC and FEV1, max did differ between the listed allergens (both p < 0.0001) but the LAR(3−7h) AUC and FEV1, max did not (p = 0.548 and 0.824, respectively). HDM did not cause a delayed recovery, measured by AUC or FEV1, max, than all other allergens during the EAR(0−3h) or the LAR(3−7h). The absolute difference between the FEV1, max and FEV1, min during the EAR(0−3h) did not differ between allergens (p = 0.180). Conclusion The FEV1, max and AUC for both the EAR(0−2h) and LAR(3−7h) had excellent correlation, with no significant difference. There was no evidence of delayed EAR(0−3h) recovery following HDM challenges.