Pattern of Airway Response to Allergen Extract of Phleum pratensis in Asthmatic Patients during and outside the Pollen Season

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Abstract
In order to evaluate the pattern of airway response to a specific bronchial provocative test (sBPT) with an extract of Phleum pratensis standardized in biological units (BU), we studied 27 patients with seasonal asthma due to grass pollen by means of allergologic evaluations, methacholine inhalation test and sBPT, outside the pollen season in all patients and, in 10 of them, also during the pollen season. We used a DeVilbiss 646 nebulizer with a dosimeter, giving increasing doses (0.01-2.5 BU) of the allergen solution and we monitored FEV1 to assess early (EAR) and late (LAR) airway responses. Outside the pollen seaseon sBPT elicited an isolated EAR in 16 and a dual asthmatic response (DAR) in 11 patients. We observed no significant difference between EAR and DAR patients as regards the provocative dose causing a 15% fall in FEV1 (PD15FEV1) methacholine, EAR (expressed by PD15FEV1 allergen) or allergologic data. There was a significant relationship between PD15FEV1 allergen and PD15FEV1 methacholine (r = 0.43, p<0.05). The reproducibility of sBPT was assessed in 11 patients outside the pollen season. The correlation coefficients between the two tests were: r = 0.91, p<0.001 for the total delivered dose of allergen during sBPT; r = 0.79. p<0.01 for PD 15FEV1 allergen; r = 0.95, p<0.001 for the maxomum percent fall in FEV1 during LAR. Ten patients repeated all tests during the grass pollent season. PD15FEV1 methacholine and baseline FEV1 decreased significantly during the pollen season, but PD15FEV 1 allergen did not change significantly during the season. Although 6 patients with a DAR outside the pollen season showed an isolated EAR during the season, the mean percent fall in FEV1 during EAR and LAR was not different between seasons.