The challenge procedure influences the extent of allergen‐induced urinary excretion of leukotriene E 4

Background Cysteinyl‐leukotrienes are central mediators in asthma and urinary leukotriene E 4 (LTE 4 ) is a reliable marker of their endogenous formation. Objective This study tested the hypothesis that the procedure used for allergen bronchoprovocation influences the bronchoconstrictor response and the amount of LTE 4 excreted following allergen challenge. Methods Seven atopic asthmatic men underwent two allergen bronchoprovocations 4 weeks apart. The same total dose of allergen was given at both sessions, cumulatively on one occasion and as a single dose at the other session. Urine was collected in hourly samples before and after challenge and LTE 4 was measured with previously validated methodology. Results The mean (±  se ) drop in FEV 1 was not significantly different between the cumulative (29 ± 2.4%) and the single dose challenge (25 ± 2.8%). There was a significant increase in post‐challenge levels of urinary LTE 4 after both sessions. The peak excretion of LTE 4 occurred 1 h following the maximal drop in FEV 1 for both challenges. However, the post‐challenge increase in urinary LTE 4 was significantly larger at the cumulative session. In fact, the net increase (post‐challenge minus prechallenge) of urinary LTE 4 was more than twofold higher after the cumulative session (AUC 0–3 h post‐challenge: 46.7 ± 8.2 vs 22.1 ± 9.8, P  < 0.05). Conclusion The peak excretion of urinary LTE 4 occurred within 2 h after the termination of either challenge but the magnitude of urinary excretion of LTE 4 was larger when cumulative challenge was performed. The findings are important to consider when designing studies where allergen‐induced urinary excretion of LTE 4 is an outcome variable.