Validation of inhalation challenge test and serum immunoglobulin G test for bird-related fibrotic hypersensitivity pneumonitis

Abstract

BackgroundThe inhalation challenge test is considered to be the item for diagnosis of hypersensitivity pneumonitis (HP) and identifying the causative antigen in patients with fibrotic HP. However, the inhalation challenge test is not widely used. ObjectiveTo evaluate the values of the inhalation challenge test by comparing with serum immunoglobulin (Ig)G test. MethodsThis was a single-center, retrospective study. The patients with fibrotic HP were diagnosed pathologically by surgical lung biopsy or transbronchial lung cryobiopsy and were assumed to have bird-related fibrotic HP if they had a history of obvious avian exposure. ResultsOn the basis of pathologic findings and history of avian exposure, 43 of 86 patients were diagnosed with having bird-related fibrotic HP. In 43 patients with bird-related fibrotic HP, 15 (35%) were positive for anti-bird IgG antibody and 36 (84%) were positive for the inhalation challenge test; in addition, the specificity of the inhalation challenge test was 67%. Patients with both positive results from inhalation challenge test and anti-bird IgG antibodies had a 2.7% decline in annual forced vital capacity (FVC) before the inhalation (P = .02). In patients with positive result from inhalation challenge test and negative result from anti-bird IgG antibodies, the annual FVC decreased by 5.8% (P = .03). FVC was not consistent in patients with positive result from the anti-bird IgG antibodies. ConclusionThe inhalation challenge test for bird-related fibrotic HP was more sensitive than the anti-bird IgG antibodies. Furthermore, the inhalation challenge test could select patients with similar disease progression.