Quantification of the dose of inhaled flour: relation with nonspecific bronchial and immunological reactivities

The aim of this study was to investigate the relationship between specific bronchial reactivity and respective nonspecific bronchial and immunological reactivities. Twenty-one patients underwent bronchial challenges with lactose and flour. The aerosol of particles was generated by a computer-controlled aerosolizer. Specific bronchial challenge results were expressed as the provocative dose of flour (PDf) that caused a 20% or 15% decrease in the forced expiratory volume in one second (FEV1). For each subject, the decrease in FEV1 observed during the challenge with flour was compared with the calculated lower limit of the 99.7% confidence interval for the lactose challenge. The subjects also underwent a nonspecific challenge with methacholine and a measurement of the specific immunoglobulin E against wheat. The inhalation of lactose did not significantly affect FEV1. Nine subjects had high reactivity to wheat flour with a PDf20 <400 microg. Five subjects had intermediate reactivity: FEV1 fell by <20% but by significantly more than that in the test with lactose. For 7 subjects, there was no significant change in FEVI for inhaled doses of flour over 1390 microg. The results for specific bronchial challenge were significantly correlated with those for the methacholine test (p<0.02). Positive skin tests and specific immunoglobulin E against wheat were observed more frequently in the high reactivity group. Specific bronchial challenge can be performed safely to establish precise dose-response curves. The provocative dose of flour causing a 20% decrease in forced expiratory volume in one second is useful for evaluating the degree of specific reactivity but is not suitable in cases of intermediate reactivity in which comparison with the lactose test is necessary. Specific reactivity is probably a function of immunological and nonspecific bronchial reactivities.