Specific IgG antibodies in chronic hypersensitivity pneumonitis

Introduction: Bird keeper9s lung (BKL) is a common form of hypersensitivity pneumonitis (HP). In patients with acute HP a positive antigen-specific IgG antibody is one of the most significant predictors for the clinical diagnosis. The differentiation of patients with chronic HP from those with idiopathic pulmonary fibrosis (IPF) can be challenging. Objectives: To compare antigen-specific IgG antibodies in patients with acute or chronic BKL and with IPF analysed with an automated quantitative fluorimetric enzyme immunoassay (FEIA). Methods: Retrospective review of patients with BKL treated in a tertiary care hospital between 2005 and 2013. Baseline clinical characteristics, the clinical course and specific IgG antibodies were analysed and compared with IPF patients. Results: 155 patients were diagnosed with BKL (90 with chronic and 65 with acute HP) and were compared with a control group of 52 IPF patients. Specific IgG antibodies to avian antigens were significantly higher in acute BKL comparing to chronic BKL (budgerigar antigens: 144 ± 58 vs. 54 ± 44 mg/l, goose feathers: 82 ± 46 vs. 41 ± 32 mg/l, pigeon antigens: 114 ± 55 vs. 57 ± 40 mg/l, parrot antigens: 125 ± 55 vs. 58 ± 37 mg/l; all p Conclusions: This study demonstrates that specific IgG antibodies to avian antigens in patients with chronic BKL are lower comparing to acute BKL but are still higher comparing to patients with IPF.