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New insights into the severity of occupational asthma

Published online: March 23, 2019

Severe asthma imposes a substantial public health burden through its major impact on patients’ quality of life and health care costs. Although sensitizer-induced occupational asthma (OA) accounts for an appreciable fraction of adult asthma, there is only scarce information on the severity of this condition.

In a study recently published by The Journal of Allergy and Clinical Immunology: In Practice, Vandenplas et al. investigated the burden and determinants of severe OA. This large retrospective cohort of 997 patients with a diagnosis of OA established by positive specific inhalation challenges during the period 2006-2015 was recruited by the European network for the PHenotyping of OCcupational ASthma (E-PHOCAS) from 20 tertiary centers located in 11 European countries. Severe asthma was defined according to the consensus definition issued by the European Respiratory Society and the American Thoracic Society as a high-level of asthma treatment (i.e. use of a high dose of inhaled corticosteroid and a second controller medication) and any one of the following criteria: 1) poor symptom control defined by daily need for a reliever medication; 2) two or more severe exacerbations requiring oral corticosteroid in the previous year; or 3) airflow obstruction on spirometry.

This cohort study revealed that a substantial fraction (16%) of patients with OA experienced severe asthma, an estimate higher than those found in studies of general adult asthma populations (4%-6%), in which the same definition of severe asthma was applied.

When the subjects were still at work, severe OA was associated with persistent exposure to unchanged (vs. reduced) levels of exposure to the causal agent and longer duration of work-related asthma symptoms. In addition, individual characteristics that included a low level of education, a history of childhood asthma and chronic sputum production were identified as risk factors for severe OA, similar to what has been reported in severe non-occupational asthma.

In the 467 (47%) subjects who were already removed from the offending exposure at the time of the diagnostic evaluation (median removal period of 7 months), the rate of severe OA declined significantly from 18% to 11%. Interestingly, in these subjects removed from exposure, individual socio-demographic and clinical characteristics (i.e. low level of education, daily sputum production, and obesity) were the predominant risk factors for severe OA.

This is the largest cohort of patients that comprehensively characterizes the severity of OA. The results demonstrate that OA is a substantial cause of severe asthma and further support the need for an early diagnosis and prompt implementation of environmental interventions in order to reduce the severity of asthma. In addition, this study shows that the determinants of severe OA include not only exposure-related factors, but also individual sociodemographic and clinical characteristics.

Overall, these findings may help clinicians to identify patients with OA who are at high risk for a more severe outcome and thereby may contribute to a more personalized management approach aimed at minimizing the health and socioeconomic impacts of the disease.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.