Individuals exposed to workplace sensitizing agents may develop an isolated sputum eosinophilic response consistent with a diagnosis of occupational eosinophilic bronchitis, even in the absence of asthma symptoms, according to study results published in The Journal of Allergy and Clinical Immunology: In Practice.
Researchers analyzed lung function measurements and sputum eosinophil counts from individuals exposed to a workplace sensitizing agent before and after a specific inhalation challenge exposure to the suspected workplace agent. Individuals were defined as having occupational eosinophilic bronchitis if they exhibited a decrease in forced expiratory volume in 1 second (FEV1) <15% during the specific inhalation challenge and an increase in sputum eosinophils ≥3% after the challenge.
Of the 259 patients, an isolated increase in sputum eosinophils after the challenge was documented in 33 individuals with negative specific inhalation challenge. Compared with control individuals with positive and negative specific inhalation challenge results, these individuals reported significantly more isolated cough at work (21% vs 0% and 5%, respectively).
The prevalence of occupational eosinophilic bronchitis was 6% in the whole cohort evaluated for work-related asthma symptoms and 14% in those with a work-related respiratory condition confirmed by the specific inhalation challenge procedure, including occupational asthma and occupational eosinophilic bronchitis. Most causal agents were low molecular weight compounds, and isocyanates accounted for nearly half of the agents.
The study authors noted that the results suggested that a substantial amount of participants who do not demonstrate any functional evidence of asthma during a specific inhalation challenge with workplace agents may develop an isolated sputum eosinophilia consistent with a diagnosis of occupational eosinophilic bronchitis.
Wiszniewska M, Dellis P, van Kampen V, et al; on behalf of the European Network for the Phenotyping of Occupational Asthma (E-PHOCAS). Characterization of occupational eosinophilic bronchitis in a multicenter cohort of subjects with work-related asthma symptoms. J Allergy Clin Immunol Pract. Published online September 10, 2020. doi:10.1016/j.jaip.2020.08.056