Occupational Asthma Reference

Hu C, Cruz M, Ojanguren I, de Homdedeu M, Gonzalez-Barcala F, Munoz X, Specific inhalation challenge: the relationship between response, clinical variables and lung function, Occup Environ Med, 2017;74:586-591,dx.doi.org/10.1136/oemed-2016-103806

Keywords: Spain, challenge, oa, methods

Known Authors

Maria Jesus Cruz, Barcelona Maria Jesus Cruz

Xavier Munoz, Barcelona Xavier Munoz

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The specific inhalation challenge (SIC) is considered the gold standard for the diagnosis of occupational asthma (OA). However, its use is not standardised, and the intensity of exposure is regulated empirically. The aim of this study was to identify clinical variables and/or pulmonary function variables able to predict the scale of patients’ response to SIC.

Material and methods
All patients who underwent SIC at our centre between 2005 and 2013 were studied. Anthropometric characteristics, atopic status, type of causal agent, latency times, pulmonary function tests and SIC results were analysed.

Two hundred and one patients (51% men) were assessed, of whom 86 (43%) had positive SIC. In the patients with positive results, 29 (34%) were exposed to high molecular weight (HMW) agents and 57 (64%) to low molecular weight (LMW) agents. Patients with a positive SIC exposed to HMW agents had a higher fall in FEV1 after SIC compared with those exposed to LMW agents (p=0.036). The type of asthmatic reaction after SIC also differed between the groups (p=0.020). The logistic regression analysis showed that patients with a higher PC20 before SIC were less likely to have severe decreases in FEV1 after SIC after adjusting for potential confounders (OR=0.771, 95% CI 0.618 to 0.961, p=0.021).

The scale of the response to SIC is influenced mainly by the degree of bronchial hyper-responsiveness, regardless of whether the causative agent is HMW or LMW, or whether the response is early or late.

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The type of asthmatic reaction after SIC also differed between the groups, with a predominance of early reactions in patients exposed to HMW agents and late reactions in those exposed to LMW agents (p=0.020). Moreover, the exposure time during SIC was longer in patients with OA due to LMW agents (p=0.003).

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