Sputum Inflammatory Patterns Are Associated With Distinct Clinical Characteristics in Patients with Occupational Asthma Independently of the Causal Agent

BACKGROUND AND OBJECTIVES: Background: Clinical heterogeneity in sensitizer-induced occupational asthma (OA) and its relationship to airway inflammatory profiles remain poorly elucidated. Objectives: To further characterize interactions between induced sputum inflammatory patterns, asthma-related outcomes, and the high- or low-molecular-weight category of causal agents in a large cohort of patients with OA. METHODS: We conducted a multicenter, retrospective, cross-sectional study of 296 patients with OA confirmed by a positive specific inhalation challenge who completed induced sputum assessment before and 24 hours after challenge exposure. RESULTS: Multivariate logistic regression analysis revealed that sputum eosinophilia ≥3% was significantly associated with a high dose of inhaled corticosteroid (OR [95%CI], 1.31 [1.11 1.55] for each 250-μg increment in daily dose), short-acting ß2-agonist use less than once a day (3.54 [1.82-7.00]), and the level of baseline nonspecific bronchial hyperresponsiveness (mild, 2.48 [1.21-5.08]; moderate/severe, 3.40 [1.44-8.29]). Sputum neutrophilia ≥76% was associated with age (1.06 [1.01-1.11]), male sex (3.34 [1.29-9.99]), absence of corticosteroid use (5.47 [2.09-15.16]), use of short-acting ß2-agonists once or more a day (4.09 [1.71-10.01]), ≥2 severe exacerbations during the previous 12 months at work (4.22 [1.14-14.99]), and isolated early reactions during the specific inhalation challenge (4.45 [1.85-11.59]). CONCLUSIONS: The findings indicate that sputum inflammatory patterns in patients with OA are associated with distinct phenotypic characteristics and further highlight the differential effects of neutrophils and eosinophils on asthma-related outcomes. These associations between inflammatory patterns and clinical characteristics share broad similarities with findings reported in nonoccupational asthma and are not related to the type of causal agent.