Incidence of severe asthmatic reactions after challenge exposure to occupational agents.

Background: Specific inhalation challenges (SICs) with occupational agents are used to establish the diagnosis and etiology of occupational asthma. The aim of this study was to assess the frequency and determinants of severe asthmatic reactions induced by various occupational agents during SICs performed using realistic methods of exposure.

Methods: The SIC records of 335 consecutive subjects with a positive SIC (ie, ≥ 20% fall in FEV1) due to various occupational agents were reviewed. Asthmatic reactions were graded as moderate when requiring repeated administration of an inhaled short-acting β₂-agonist (SABA) and severe when requiring repeated SABA and systemic corticosteroids.

Results: Overall, 68 of the 335 subjects (20%) required an inhaled SABA during the SICs. The multivariate logistic regression analysis showed that the need for an inhaled SABA increased when the SIC involved a low-molecular-weight agent (LMW) (OR, 2.47; 95% CI, 1.43-4.28) and marginally so when the subjects required regular treatment with an inhaled corticosteroid (OR, 1.62; 95% CI, 0.93-2.80). The severity of asthmatic reactions was graded as moderate in 12% and severe in 3% of the subjects. Of the 10 severe reactions, five developed after exposures ≤ 5 min. Multivariate logistic regression analysis showed that challenging subjects with a LMW agent was the only significant determinant for the development of moderate/severe reactions (OR, 3.05; 95% CI, 1.62-5.73).

Conclusions: Challenges with LMW agents are associated with a higher risk of an asthmatic reaction requiring pharmacologic treatment. This study may provide useful guidelines for further improving the safety of SICs.