Long-term clinical follow-up of irritant-induced occupational asthma.

Abstract

Background: Occupational exposure to irritants is associated with poor asthma control, but the long-term clinical characteristics of irritant-induced occupational asthma (IIA) are poorly known.

Objective: To evaluate whether any distinguishable features contribute to IIA patients' poor outcomes and whether clinical characteristics change over time.

Methods: We re-evaluated 28 IIA patients with a median of 6.8 years (IQR 4.6-11.1) after their diagnosis at the Finnish Institute of Occupational Health in 2004-2018. We measured their lung function, non-specific bronchial hyper-responsiveness, inflammation profile and exercise capacity using an ergometric bicycle test. The participants also underwent an Asthma Control Test (ACT) and responded to questionnaires assessing their laryngeal hypersensitivity (LHQ) and dysfunctional breathing (Nijmegen Questionnaires, NQ).

Results: At follow-up, 22 (79%) participants used inhaled corticosteroids, 4 (14%) had asthma exacerbation within 1 year, 11 (39%) had ACT<20 (ie, poor asthma symptom control), 7 (26%) had abnormal spirometry and 8 (36%) had a positive methacholine challenge test result. 17 (61%) participants showed at least one elevated eosinophilic inflammation marker. Six (23%) had an abnormal LHQ score and 7 (26%) had an abnormal NQ score. 15 (58%) participants showed reduced physical capacity that was related to extensive asthma medication, poor asthma symptom control and acute IIA phenotype. A higher ACT score was the only significant change between diagnosis and follow-up (p=0.014).

Conclusion: Most of the IIA patients had normal lung function at follow-up, which had only changed a little over time. Reduced physical capacity was a common finding and appears to be related to poor asthma symptom control.