Effects of cigarette smoking on diagnostic tests for work-related hypersensitivity pneumonitis: Data from an outbreak of lung disease in metalworkers

Background It is widely believed that development of hypersensitivity pneumonitis (HP) is forestalled in cigarette smokers. We encountered the largest outbreak of HP in metalworkers yet reported [Hodgson et al. (2001): Am J Ind Med 39:616-628] and subsequently did a chart review of the 61 patients seen in connection with the outbreak [Dangman et al. (2002a): Am J Resp Crit Care Med 165(8):A528; Dangman et al. (2002b): Am J Ind Med 42:150-1621, developing a diagnostic index for this disease. Methods A re-examination of data from the chart review was carried out to explore possible effects of cigarette smoking on the clinical tests used to diagnose HP [Hodgson et al. (2001): Am J Ind Med 39:616-628]. Results Cigarette smokers with HP were less likely than non-smokers with HP to develop crackles in the lungs, elevated erythrocyte sedimentation rates (ESRs), and restrictive spirometry Smoking habits had little effect on diffusion capacity and alveolar-arterial oxygen gradients in the patients with HP. Smokers were more likely to have abnormal gallium scans than non-smokers. Conclusions It appears that cigarette smoking can affect the physical examination findings, spirometry, and ESR changes associated with HP making these tests less sensitive and specific, and potentially obscuring the diagnosis. Such changes may contribute to the apparent "protective" effect of smoking on the development of HP. Am. J. Ind. Med. 45:455-467, 2004. Published 2004 Wiley-Liss, Inc.