The following is a summary of “Impact of ongoing treatment with inhaled corticosteroids during specific inhalation challenges for diagnosing occupational asthma,” published in the July 2024 issue of Allergy and Immunology by Lavoie et al.

Specific inhalation challenge tests (SIC) remain the gold standard for diagnosing sensitizer-induced occupational asthma (SIOA) despite recommendations from the European Respiratory Society to discontinue inhaled corticosteroids (ICS) 72 hours before testing. The study aimed to investigate the impact of ongoing ICS treatment during SIC on the maximum decrease in FEV₁, changes in methacholine PC₂₀, and sputum eosinophil counts following exposure to the suspected allergen.

Researchers conducted a retrospective analysis of data from patients referred to the center for suspected SIOA between 1999 and 2022. They compared SIC outcomes between two groups: those receiving ICS during the test and those who were steroid-naïve. Specifically, the study group assessed differences in the maximum fall in FEV₁, alterations in methacholine PC20, and changes in sputum eosinophil counts.

A total of 671 individuals underwent SIC, with 318 on ICS treatment and 353 steroid-naïve. The frequency of positive SIC results was significantly higher in the ICS-treated group (39.6%) compared to the steroid-naïve group (27.5%, p<0.001). Despite this, ICS treatment did not significantly alter SIC outcomes. There were no notable differences in methacholine PC₂₀ changes or sputum eosinophil percentages post-challenge between the ICS-treated and steroid-naïve groups.

Ongoing ICS treatment during SIC does not affect the likelihood of an asthmatic reaction or the degree of airway hyperreactivity and eosinophilic inflammation following exposure to a suspected sensitizer. These findings suggest that ICS therapy does not interfere with the diagnostic accuracy of SIC in patients with prolonged ICS use.

Source: sciencedirect.com/science/article/abs/pii/S2213219824007712