Introduction

Use of inhaled corticosteroids (ICS) prior to allergen inhalation challenge can blunt the asthmatic reaction. Thus, guidelines on occupational asthma (OA) suggest discontinuing ICS 72h before testing. However, there is little real-world data on their impact on the results of specific inhalation challenges (SIC).

Aims and objectives

To assess the impact of ongoing treatment with ICS on the maximum fall in FEV1 and the change in airway responsiveness following exposure to the offending agent

Methods

We conducted a retrospective study using a database of 671 subjects who underwent SIC in our laboratory between 1999 and 2022. The database comprises clinical and functional data. The total dose of ICS was administered 12h before each day of testing. Logistic and linear regression models were used to assess the effects of ICS on the maximum fall in FEV1 and the change in PC20 after SIC while controlling for confounders.

Results

671 subjects were assessed. 318 were taking a mean (±SD) of 653 (±338) mcg of ICS and 353 were steroid naïve. Subjects taking ICS had lower baseline FEV1 and PC20. 223 (33%) subjects had a positive SIC. The mean maximum fall in FEV1 after exposure was higher in subjects with ICS (13.1±11.4%) than in steroid naïve subjects (10.9±11.5%) p=0.015. Change in PC20 after exposure was similar in both groups. ICS did not appear to be a significant factor influencing the maximum fall in FEV1 (OR 1.55 95% CI 0.96-2.50) or change in PC20 (OR 0.96 95% CI 0.60-1.31) after SIC.

Conclusion

Ongoing treatment with ICS during SIC does not appear to reduce the maximum fall in FEV1 or change in airway responsiveness. ICS can be continued during SIC without affecting the results.