What is the performance of the methacholine challenge in occupational asthma?


Published Online: July 29, 2015

The diagnosis of occupational asthma (OA) is often a challenge and needs a stepwise approach. One step of this approach is to determine the presence of an increased non specific bronchial responsiveness (NSBR) by a methacholine challenge. Recent guidelines on work-related asthma state that the absence of NSBR can be used to rule out active OA. However, this statement had not been verified in a large population.

In a study published in The Journal of Allergy and Clinical Immunology (JACI), Pralong et al. evaluated the performance of the methacholine challenge for the diagnosis of OA by calculating positive and negative predictive values (PPV and NPV, respectively) in 1,012 workers referred for a suspicion of OA.

The researchers reported a NPV of 95.2%, which means that a negative methacholine, and therefore the absence of NSBR, challenge allows excluding the diagnosis of OA in more than 95% of cases. When considering all workers tested by a methacholine challenge at least once while at work (479 subjects), the NPV increased to 97.7%.

These findings suggest first that the absence of NSBR in a worker still exposed to the causative agent at work makes the diagnosis of OA very unlikely. Second, they emphasize the importance of performing the diagnosis workup when the worker is still at work.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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