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

Abstract

BackgroundHouse 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 methods has not been previously investigated.AimsWe aimed to measure the correlation between FEV1, max and AUC during the early asthmatic response (EAR) and the late asthmatic response (LAR), and to determine if the EAR recovery period for HDM would be longer than other allergens (cat, grass, horse, and ragweed).MethodsWe retrospectively calculated the AUC and correlation between FEV1, max and AUC during the EAR(0-2 h) and LAR(3-7 h) for each allergen. We compared EAR(0-3 h) and LAR(3-7 h) FEV1, max, AUC and absolute difference in FEV1, max to the most recovered FEV1 (FEV1, min). 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.ResultsCorrelation between the FEV1, max and AUC during the EAR(0-2 h) (n = 221) was 0.807, and was 0.798 during the LAR(3-7 h) (n = 157 of 221), (difference p = 0.408). The EAR(0-3 h) AUC and FEV1, max did differ between allergens (both p < 0.0001) but the LAR(3-7 h) AUC and FEV1, max did not (p = 0.548 and 0.824, respectively). HDM did not have a larger AUC or FEV1, max, than all other allergens during the EAR(0-3 h) or the LAR(3-7 h). The absolute difference between the FEV1, max and FEV1, min during the EAR(0-3 h) did not differ between allergens (p = 0.180).ConclusionThe FEV1, max and AUC for both the EAR(0-2 h) and LAR(3-7 h) had excellent correlation, with no significant difference. Thus, significant bronchoconstriction will likely result in a longer recovery period. There was no evidence of delayed EAR(0-3 h) recovery following HDM challenges, so HDM did not induce a larger response compared to all the other allergens examined.Registration: Not registered. This is not a clinical trial. (This study is a retrospective analysis of data collected during several registered trials.)