Inhalation Challenge With Bovine Dander Allergens. Part 2
October 23rd, 2020 by admin - Leave a comment
For several reasons, the selection of patients for SICs may be especially demanding in farmers. First, the suspicion of occupational asthma easily arises in them. One in every three dairy farmers complains of lower airways respiratory symptoms, and as many as 14% of dairy farmers in Finland show a positive skin-prick test (SPT) response for bovine allergens. Second, the demonstration of a temporal relationship between asthmatic symptoms and work exposure is difficult in dairy farmers, as they actually live in their working environment and usually work 7 days a week rather than 5 days. Even if a temporal relationship could be demonstrated, it does not necessarily indicate the presence of occupational asthma since preexisting asthma also can be aggravated in the dusty environment of a farm. This far, even a negative response to an SPT with bovine allergens has not been an exclusion criterion for an SIC with bovine dander allergens (bSIC), since subjects with a negative response to an SPT also have been reported to respond to bovine dander aller-gens. These facts have led to a high number of referrals for bSICs in our institute. However, the majority of the results of these challenges are negative, and thus there is a need to improve the means of selection of subjects who should undergo a bSIC.
In this study, we examined whether histamine challenge, mannitol challenge, exhaled nitric oxide (NO) measurement, serum bovine-specific IgE (bIgE) measurement, or SPT with bovine allergens could help in identifying which patients should be subjected to bSIC.
Materials and Methods
Subjects
We recruited 38 consecutive dairy farmers who were referred to our laboratory because of a suspicion of occupational asthma due to bovine allergens. All had been referred by a respiratory physician, and the suspicion was based on a temporal relationship between work in a cow shed and asthmatic symptoms and/or ambulatory peak expiratory flow (PEF) variations. Exclusion criteria were unstable asthma, FEV1 < 65% of predicted, and respiratory tract infection within the last 6 weeks. One patient was excluded because he had responded positively to a sham challenge. The basic characteristics of the remaining 37 subjects are given in Table 1. Before hospital admission, 30 patients had a doctor’s diagnosis of asthma. SPTs for common and agricultural allergens (ie, cow, storage mites, rye, oat, wheat, and barley) had been performed before the study (Soluprick SQ; ALK Abello; Horsholm, Denmark).
The subjects were asked not to work in the cow shed and to measure their PEF (Mini Wright; Clement Clarke International; Harlow, UK) twice daily during the week before hospital admission. They were also asked to withhold therapy with inhaled steroids for 1 week, with leukotriene receptor antagonists for 3 days, with antihistamines for 3 days, with inhaled long-acting P2-adrenoreceptor agonists for 48 h, and with anticholinergic agents for 8 h prior to hospital admission.