Anti-chicken and anti-pigeon immunoglobulin G testing in patients with bird-related fibrotic hypersensitivity pneumonitis.

Background: One of the inciting antigens for fibrotic hypersensitivity pneumonitis (HP) is avian. It is controversial whether chickens are the inciting antigen of bird-related fibrotic HP; the anti-chicken immunoglobulin (Ig) G testing for bird-related fibrotic HP patients was investigated.

Methods: Anti-pigeon IgG and anti-chicken IgG antibodies by mainly enzyme-linked immunosorbent assay (ELISA) were measured in patients with bird-related fibrotic HP. We included bird-related fibrotic HP patients who had undergone histopathological examination and who had a positive inhalation challenge test.

Results: We included 44 patients with bird-related fibrotic HP and 48 with fibrotic interstitial lung diseases other than fibrotic HP. The mean titers of anti-pigeon IgG antibody by ELISA were 0.659 ± 0.381 and 0.494 ± 0.187 in the bird-related fibrotic HP and control groups, respectively (p = 0.012). Those of anti-chicken IgG antibody were 0.345 ± 0.189 and 0.376 ± 0.167, respectively (p = 0.457). No significant correlation was found between anti-pigeon IgG testing by ELISA and anti-chicken IgG testing (r = 0.45, p = 0.45). In patients with bird-related fibrotic HP, annual FVC changes were significantly different (p = 0.001), with the higher titer group improving by 0.4 % and the lower titer group decreasing by 4 %. Similarly, no significant differences in annual FVC changes were observed between the higher and lower anti-chicken IgG antibody titer groups among bird-related fibrotic HP patients.

Conclusion: Serum IgG testing for chicken serum was less effective in diagnosing or predicting the disease progression of bird-related fibrotic HP than that for pigeon serum.