Significance of precipitins and asymptomatic lymphocytic alveolitis: a 20-yr follow-up

What is the significance of serum precipitins and lymphocytic alveolitis in a healthy subject exposed to antigens responsible for hypersensitivity pneumonitis (HP)? This study was done to evaluate the 20-yr outcome of asymptomatic dairy farmers with or without precipitins or lymphocytic alveolitis in their bronchoalveolar lavage (BAL). Twenty-seven of the initial 43 farmers were restudied. Of the missing 16, 11 refused the follow-up, three had died and two could not be located. The restudied farmers had a clinical evaluation, lung function tests and a high resolution computed tomography (HRCT). Only one subject, an asthmatic, had dyspnoea, none described present or past symptoms suggestive of HP. Of those who were no longer on the farm, none had quit because of respiratory problems. Lung function changes were as expected with aging. The only difference was that farmers with positive precipitins had a statistically significant greater decrease in their forced expiratory volume in one second than the sero-negative farmers. Four HRCTs showed signs of minimal parenchymal abnormalities; these were not more prevalent for subjects with or without precipitins or BAL lymphocytosis. Serum precipitins and asymptomatic lymphocytic alveolitis in an asymptomatic, exposed dairy farmer have no clinically meaningful long-term consequences.