Predictors of patterns of response following specific inhalation challenge testing with low molecular weight agents.

Abstract

Introduction: Little is known about the mechanisms separating early from late specific inhalation challenge (SIC) reactions. Most studies have been with IgE mediated reactions where bigger immediate reaction and greater non-specific reactivity are determinants of the subsequent late reaction. We have looked for predictors of late asthmatic reactions following SIC with mostly low molecular weight agents. Methods: 53 workers with positive SIC to occupational agents between 2006 and 2015 were included. Non-specific bronchial reactivity (NSBR) was measured pre and post SIC. The % fall in FEV1 during immediate reactions and NSBR were compared between those with and without subsequent late reactions. Results: 20 workers had isolated immediate reactions, 24 had dual (immediate and late) reactions and 9 had isolated late reactions. Immediate SIC reactors had more NSBR (p=0.03), and greater falls in FEV1 during the immediate reaction than those with dual reactions (p=0.002). Post SIC responsiveness increased more often following dual reactions, the differences (compared with immediate reactors) were not statistically significant (p=0.27). Workers with isolated late reactions were less likely to be taking inhaled corticosteroids during SIC (p=0.012). Conclusions: Bigger immediate reactions and greater NSBR did not predispose to dual reactions. Inhaled corticosteroids during SIC were less frequent in isolated late reactors, but similar in those with immediate or dual reactions.