Usefulness of serum bird specific antibody levels in patients with interstitial pneumonia

Abstract

Backgrounds: Definitive diagnosis of bird related chronic hypersensitivity pneumonitis (BRCHP) is difficult because of its complicated diagnostic criteria. Therefore, BRCHP has been reported to be misdiagnosed with interstitial pneumonia (IP). Recently the level of IgG antibody (Ab) against pigeon has been able to be measured by the ImmunoCap system. Here, we conducted a retrospective study to investigate the usefulness of serum pigeon IgG Ab in patients with IP. Methods: Medical records of patients who were measured of serum pigeon IgG Ab and diagnosed with IP were retrospectively reviewed from Jun 2014 to Dec 2015. Patients with previous diagnosis of hypersensitivity pneumonitis (HP) were excluded. We investigated the relation between the levels of serum pigeon Ab and clinical outcomes. Results: The clinical diagnosis of 113 patients were as follows (number of patients); IPF 12, NSIP 32, COP 4, pleuroparenchymal fibroelastosis 5, CPFE 9, collagen vascular disease related IP 32, and drug induced IP 19. Serum pigeon Ab levels were 16.6±11.1μg⁄ml. Kaplan–Meier analysis showed that time to first exacerbation was significantly shorter in patients with high levels of pigeon Ab (>22.3μg⁄ml) compared with low or middle levels ( P = 0.025). Removal of bird related antigens accomplished the improvement of clinical symptoms or radiological findings more frequently in patients with high levels of pigeon Ab (>22.3μg⁄ml) compared with low or middle levels ( P = 0.015). Conclusions: Patients with high levels of pigeon Ab had higher risk of exacerbation and potential improvement by removal of bird related antigens. Serum pigeon Ab may be a useful biomarker to discover BRCHP among patients with IP.