The Amount of Avian Antigen in Household Dust Predicts the Prognosis of Chronic Bird-related Hypersensitivity Pneumonitis

Rationale: Bird-related hypersensitivity pneumonitis is induced by inhalation of avian antigen. Evaluation to avoid repeated exposure to avian antigen is a key part of the treatment for bird-related hypersensitivity pneumonitis. It can be difficult, however, to reliably evaluate exposure to the antigen because bird-related hypersensitivity pneumonitis in its chronic form may be caused by unrecognized and indirect exposure. Objective: The purpose of the present study is to establish a method for measuring environmental avian antigen in patients with chronic bird-related hypersensitivity pneumonitis and to evaluate the clinical utility of the method. Methods: The amount of avian antigen was measured in samples of dust collected from the household environments of patients with chronic bird-related hypersensitivity pneumonitis. The patients whose clinical progress could be followed by periodic pulmonary function tests for 1 year were classified into a deterioration group and a stable group. Age, sex, smoking status, FVC % predicted, and the amount of avian antigen in household dust samples at the diagnosis of bird-related hypersensitivity pneumonitis, as well as survival, were determined and evaluated for each group. The total number of subjects was 23. Measurements and Main Results: The clinical condition deteriorated in 11 patients and remained stable in 12. The amount of avian antigen in household dust samples was significantly higher for the deterioration group than for the stable group. In logistic regression analysis, avian antigen was the only variable found to be significant for distinguishing between the two groups. The patients with higher amounts household dust avian antigen had a poor prognosis in the survival analysis. Avian antigen was the only variable to significantly influence the prognosis of chronic bird-related hypersensitivity pneumonitis. Conclusions: The levels of exposure to avian antigen were related to disease progression and prognosis in chronic bird-related hypersensitivity pneumonitis.