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Workers with asthma‐like symptoms should have their sputum checked for eosinophils as well as having other, standard, respiratory tests, say doctors who have recently reported two new causes of eosinophilic bronchitis in the workplace.
Their assertion rests on two cases associated with workplace exposure to methylene diphenyl isocyanate in a foundry worker and wheat flour in a male baker. The 44 year old foundry worker, who had been at the foundry for eight years, had developed a non‐productive chronic cough in the past six months, whereas the 41 year old baker had acquired the same symptoms in the previous two years, after 10 years' exposure to flour.
The proportion of sputum eosinophils in each man was directly related to periods of exposure, non‐exposure, and bronchial challenge with isocyanate (35% after a work shift; 0% not exposed; 60% after challenge) or flour (40%; 0%; 54%), respectively, and it mirrored the respiratory symptoms as they varied with exposure. FEV1 values did not change during the 24 hour observation period after challenge. Both workers presented with non‐productive cough with no wheeze or dyspnoea, which was directly related to occupational exposure in their respective workplaces. Standard blood and lung function tests gave normal results on initial testing.
So far, eosinophilic bronchitis has two other proven occupational causes: natural rubber latex and acrylates. The condition presents as a chronic cough with increased proportion of sputum eosinophils (>3% of non‐squamous epithelial cells) but no variable airflow obstruction or airway hyper‐responsiveness.
Di Stefano F, et al. Thorax 2007;62:368–370.
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Copyright © 2007 BMJ Publishing Group