Factors associated with positive inhalation provocation test results in subjects suspected of having chronic bird-related hypersensitivity pneumonitis

Abstract

Background: Chronic bird-related hypersensitivity pneumonitis (BRHP) is often misdiagnosed as other interstitial lung diseases. While the utility of the inhalation provocation test (IPT) has been reported, the test is not commonly performed. In this study, we aimed to identify significant clinical variables associated with positive inhalation provocation test results in subjects suspected of having chronic BRHP. This would help clinicians decide whether to perform IPT in patients suspected of having chronic BRHP in real-life practice.

Methods: We retrospectively evaluated 107 patients who underwent the IPT for suspected chronic BRHP. We used the IPT as the gold standard diagnostic tool for chronic BRHP.

Results: Specific antibodies against pigeon dropping extract were documented in 52% of the IPT-positive patients but also in 38% of the IPT-negative patients (p=0.172). By using the logistic regression model, three significant predictors of IPT results were identified as follows: (1) a history of raising birds (odds ratio [OR] 3.112), (2) exposure to birds from the surrounding environment (OR 7.321), (3) white blood cell count (×10²/μl; OR 0.959).

Conclusions: This study demonstrates that current or past exposure to avian antigens is a positive predictor of positive IPT results in patients suspected of having chronic BRHP.

Keywords: Bird; Chronic hypersensitivity pneumonitis; Inhalation provocation test; Interstitial lung disease.