Allergen challenge dose-response slope

Bronchial allergen challenges: doubling or quadrupling dose steps?

Inhalation challenges with allergens are considered the gold standard for the diagnosis of occupational asthma. However, no standardized methods are available. One open question is the degree of dose augmentation in the stepwise challenge protocols. Recently, it was recommended to increase the allergen concentrations by no more than doubling between dosing steps for safety reasons. We analyzed retrospectively our dosimeter allergen challenges performed with quadrupling dose steps during the last 10 years. Allergens were inhaled by an APSpro dosimeter and a DeVilbiss 646 nebulizer. The test was terminated after a fall of FEV(1) of at least 20%. Seventeen tests in 13 subjects were considered positive. The mean FEV(1) decreases 10 and 20-30 min after the last allergen dose were 26.7 ± 6.4 and 26.2 ± 6.5%baseline, respectively. Terminal dose response slopes did not differ between doubling (Cockcroft and Davis, J Allergy Clin Immunol, 122:1034-1035, 2008) and quadrupling doses, nor were there any differences concerning the maximal responses. The results suggest that quadrupling dose steps may be an acceptable alternative, without serious increase in risk of severe asthmatic reactions. We assume that by shortening the test duration, physicians might choose lower starting doses and thus make allergen inhalation challenges safer.