Workplace specific challenges as a contribution to the diagnosis of occupational asthma

¹ Dept of Chest Medicine, Hôpital du Sacré-Cur de Montréal

^* To whom correspondence should be addressed. E-mail: manon.labrecque{at}UMontreal.CA.

	Abstract

The diagnosis of occupational asthma (OA) can be made by exposing workers to the relevant agent either in a hospital laboratory through specific inhalation challenges (SIC) or at the workplace. As suggested by several authors, workers with negative laboratory SIC can be monitored at the workplace under supervision. Aim: Assess the frequency of and identify factors associated with a positive workplace reaction in workers with negative SIC in the laboratory.

We examined the results of workplace challenges in 99 workers who underwent negative SIC between 1994 and 2004. A positive reaction either in the SIC or in the workplace was a sustained fall in FEV₁ of 20% or more.

Twenty-two workers (22.2%) showed positive responses at the workplace. These subjects more often had increased baseline methacholine responsiveness (90.5% vs 67.6%, p=0.05). They also underwent more days of SIC testing (4.9 vs 3.3 days, p=0.004) and were exposed more often to two or more agents (56% vs 28.4%, p=0.002) and for a longer period (363.3 min vs 220.4 min, p=0.002) in the laboratory.

This study illustrates the usefulness of workplace monitoring of airway function in the investigation of OA and identifies factors that are more often associated with a positive reaction.