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.

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.