Prognostic factors in patients with reactive dye or isocyanate-induced occupational asthma after avoidance of causative agents

Lee, Sang Fok; Kim, Yoon Keun; Kim, Woo Kyung; Son, Jee Woong; Cho, Sang Heon; Min, Kyung Up; Kim, You Young

Abstract

BACKGROUND: Although occupational asthma is defined as a reversible airway obstruction causally related to exposure in the working environment, many occupational asthmatics complain of asthmatic symptoms despite avoidance of the causative agent. Subjects and methods. Twenty-nine patients with occupational asthma who had been confirmed by specific bronchial challenge with reactive dye or isocyanates and had avoided the causative agent for at least 6 months were included in this study. A questionnaire about asthmatic symptoms and medication requirements, a lung functiontest, and a methacholine bronchial provocation test were performed.
RESULTS
Asthmatic symptoms at follow-up were remitted in seven (41.2%) isocyanate-induced asthmatics, but none with reactive dye-induced asthma were remitted. At follow-up, the symptom-medication score and FEV1 were significantly improved in isocyanate-induced asthmatics than in those with reactive dye-induced asthma, but the geometric mean of PC20-methacholine was not different between the two groups. Among 17 isocyanate-induced asthmatics, a duration from symptom onset to avoidance was significantly shorter in the remission group than in the nonremission group, although the symptom-medication scores, FEV1 (% predictive value) and logPC20-methacholine at an initial diagnosis, and follow-up period defined as duration from avoidance to follow-up, showed no difference between the two groups.
CONCLUSION
The outcome of occupational asthma may be determined by the causative agents and the duration from onset of asthmatic symptoms to avoidance.