Occupational Asthma Reference
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Boulet L-P, Gauvreau G, Boulay M-£E, O'Byrne PM, Cockroft DW,
Allergen-induced early and late asthmatic responses to inhaled seasonal
and perennial allergens,
Clin Exp Allergy,
2015;45:1647-1653,
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Keywords: challenge, late reaction, Canada, nsbr, IgE, non-occupational
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Abstract
Background
The allergen bronchoprovocation (ABP) test is a validated model to study
asthma pathophysiology and response to treatments. The inhibitory effect of agents on the allergen-induced late asthmatic response (LAR) is a predictor of their ef?cacy in asthma treatment. However, it is dif?cult to predict the magnitude of a LAR, which may vary according to immune responsiveness and the type of allergen used for ABP.
Aim
To determine the relationship between the magnitudes of early asthmatic response
(EAR) and LAR in mild asthmatic subjects according to the type of allergen inhaled and its determinants.
Methods
This is a retrospective analysis of a large database of ABPs, all performed with a
common standardized methodology. Patients were either challenged with house dust mites (HDMs), animals or pollens allergens. EAR was de?ned as a = 20% fall in forced expiratory volume in 1 s (FEV1) < 3 h following ABP and LAR as a = 15% fall in FEV1 between 3 and 7 h post-ABP. The ratio of EAR % fall in FEV1/LAR % fall in FEV1 was compared between the groups of subjects according to the allergen used for ABP.
Results
Data from 290 subjects were analysed: 87 had an isolated EAR and 203 had a
dual response (EAR + LAR). Dual responders had a signi?cantly lower baseline PC20,a
more marked fall in FEV1 at EAR, and a trend towards higher baseline sputum eosinophil percentages. The ratio of EAR over LAR was signi?cantly lower in HDM compared with pollen ABP, indicating a larger LAR for a similar EAR. No correlations were observed between the ratio of EAR over LAR and the various parameters recorded in the different groups analysed.
Conclusion
Different mechanisms may be involved in modulating the magnitude of the
LAR, according to the type of allergen. HDM seems to induce a stronger LAR than pollens, animal allergens being intermediary in this regard.
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Comments
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In IgE mediated non-occupational asthma the main feature separating an immediate from a dual reaction appears to be the magnitude of the immediate reaction.
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