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Exposure to high-molecular-weight agents influenced occupational asthma, FENO

An increase in fractional exhaled nitric oxide was more strongly associated with occupational asthma caused by high-molecular-weight agents than with low-molecular-weight agents, according to recent study results.

Catherine Lemiere, MD, MSc, of the department of chest medicine, Sacré-Coeur Hospital, Montreal, and colleagues conducted a prospective, observational study of 178 adults who underwent specific inhalation challenge (SIC) from 2006 to 2012 to determine possible occupational asthma (OA). Assessments of fractional exhaled nitric oxide (FENO) and sputum eosinophil counts were conducted at baseline and 24 hours after SIC.

Catherine Lemiere

A two-step cluster analysis was conducted in a subgroup of OA patients. A multivariate logistic regression analysis was performed to identify variables associated with FENO increase in these patients.

Ninety-eight patients (mean age, 40.05 years; 61.2% men) had a positive SIC test. Three clusters were identified in the OA subgroup, with clusters one and two mainly composed of patients exposed to high-molecular-weight (HMW) agents and cluster three exclusively composed of patients exposed to low-molecular-weight (LMW) agents.

Although SIC results were positive, no increase in FENO levels was observed for patients in cluster three who were exposed only to LMW agents.

“The molecular weight of the agent (HMW vs. LMW) was the only factor associated with an increase in FENO (OR=4.2; 95% CI, 1.1-16.8) in subjects with a positive SIC,” the researchers said. “Although the mechanisms underlying these different patterns of FENO response between HMW and LMW agents remain to be explored, the results of this study provide useful information for the clinical investigation of work-related asthma using FENO measurements as an indirect marker of airway inflammation.”

Disclosure: See the study for a full list of relevant financial disclosures.