Serum precipitins in hypersensitivity pneumonitis: association with patients’ characteristics and disease type

Background Antigen specific immunoglobulins G (IgGs), also known as precipitins, can be detected in serum of patients with hypersensitivity pneumonitis (HP) and have an established diagnostic value. Our study aimed at investigating a possible correlation of serum precipitins with clinical characteristics, lung function impairment and HP type. Patients and methods Consecutive subjects with HP from a single center were retrospectively studied. Precipitins were centrally measured at first presentation (baseline) by using ImmunoCAP Specific IgG assay. Demographics, clinical characteristics and lung function tests were collected. Results 130 patients (62 F, age 70±11 y) were studied: 115 had chronic HP, of them 60 had the fibrotic form. 71% tested positive for pigeons (mean, SD: 70.9±43.1 mg/l), 45% for canaries (43.8±15.2 mg/l); 44% for budgies (50.1±36.5 mg/l), 24% for aspergillus fumigatus (63±49.1 mg/l) and 12% for micropolyspora faeni IgG (32.5±15.7 mg/l), 39 (61%) had multiple IgG positivity. A weak inverse correlation between FVC% pred, but not DLco, and pigeons IgG concentration at baseline was observed (r=-0.247, p=0.017). No differences in IgG concentration were found according to age, BMI, gender and smoking status. Pigeons and micropolyspora IgG concentrations, but not the other types, were significantly lower in patients with fibrotic vs non-fibrotic HP (65±45 vs 102±50, p=0.015 and 24.3±5.4 vs 42.2±9.1, p=0.004, respectively). <bold>Conclusions:</bold> Lower concentrations of pigeons and micropolyspora IgG in serum of fibrotic vs non-fibrotic HP patients suggest a potential clinical relevance of these antibodies.