Abstract

Background
Occupational eosinophilic bronchitis (OEB) has been described only as anecdotal case reports.

Objective
We investigated the clinical and inflammatory characteristics of subjects with OEB identified in a cohort of subjects who completed a specific inhalation challenge (SIC) with occupational agents.

Methods
In this retrospective multicenter study, OEB was defined by: 1) a fall in FEV1 <15% during the SIC and the absence of nonspecific bronchial hyperresponsiveness (NSBH) both before after the SIC; and 2) a post-challenge increase in sputum eosinophils =3%. The subjects who fulfilled these criteria were compared to 226 subjects with a negative SIC and 30 subjects with a positive SIC who failed to show baseline NSBH.

Results
An isolated increase in post-challenge sputum eosinophils was documented in 33 of 259 subjects (13%) with a negative SIC. These subjects reported significantly more often an isolated cough at work compared with the negative and positive SIC controls. When compared with positive SIC controls, the subjects with OEB experienced less frequently work-related wheezing and reported a shorter duration of symptoms at work. The sensitivity of the post-SIC increase in FeNO in identifying OEB among subjects with a negative SIC was low, ranging from 43% to 24% using cutoff values of 8 ppb to 17.5 ppb, while the specificity was high (90% to 97%).

Conclusion
This study highlights the relevance of induced sputum analysis in the investigation of work-related asthma symptoms in order to identify isolated increases in sputum eosinophils that are consistent with a diagnosis of OEB.

Full Text

Comments

Eosinophilic bronchitis was defined as an increase in sputum eosinophilia of >=3% 24 hours post SIC, with no NSBR and a fall in FEV1 <15%. The eosinophilic bronchitis group had more cough, higher FEV1 and a shorter period of work-related symptoms than those with a positive SIC, raising the possibility that this is an early stage of eosinophilic occupational asthma rather than a separate disease. Measuring sputum eosinophilia is unpleasant for the patient and time consuming for the staff, unfortunately this study showed that increases in FeNO (which is much easier to measure) had a poor sensitivity for detecting the >3% increase in sputum eosinophilia (an increase of 8ppb had a specificity of 90% and a sensitivity of 43%). This study critically depends on the 15% cut off for a positive SIC, the FEV1 changes post SIC are not given in the paper. I would be much happier if the disease was defined by changes found following usual exposures at work, rather than the artificial (but controlled) exposures in the laboratory.

9/24/2020