Effect of contact avoidance or treatment with oral prednisolone on bronchoalveolar lavage surfactant protein A levels in subjects with farmer's lung

Background - Surfactant protein A (SP-A) acts as an immune system modulator in the lungs and may therefore be involved in the pathogenesis of hypersensitivity pneumonitis. Methods - The levels of SP-A in bronchoalveolar lavage (BAL) fluid were measured in 20 subjects with acute farmer's lung, 16 asymptomatic dairy farmers, and 14 normal controls. Eight patients had a second evaluation after one month of treatment by either contact avoidance (n = 3) or oral prednisolone (20 or 25 mg/day, n = 5). Chest radiographs and lung function measurements were also obtained in all farmers, twice in those re-evaluated after treatment. Results - Patients with acute farmer's lung had significantly higher levels of SP-A than asymptomatic farmers and normal controls (p = 0.005) with mean (SE) values of 1.43 (0.29) mu g/ml, 0.62 (0.09) mu g/ml, and 0.68 (0.11) mu g/ml, respectively. In eight subjects tested after one month of treatment the level of SP-A was unchanged although all were clinically improved. No correlations were seen between levels of SP-A in BAL fluid and numbers of BAL cells, lung function measurements, or chest radiographic scores. Conclusion - Although the level of SP-A is increased in the BAL fluid of patients with acute farmer's lung, it is not correlated with clinical abnormalities of this disease.