C39-28 Role of Immunoglobulin Measurement in Idiopathic Pulmonary Fibrosis and Hypersensitivity Pneumonitis

Rationale Predictive value of serum immunoglobulins (Ig) in patients with IPF or HP has not been established with data suggesting worse survival with elevation in IgA in IPF. Increased IgG is noted in HP but the impact of other immunoglobulins is not known. We hypothesize that immunoglobulins can be a prognostic marker in IPF and HP. Methods Retrospective review of patients from a single center diagnosed with IPF and HP between 2015-2024 who had immunoglobulins obtained at the time of diagnosis was performed. Results A total of 205 patients with IPF and 80 patients with HP were identified. The mean age for IPF was 73.6 years ± 8.8 with a male predominance (72.7%) while mean age for HP was 70.9 ± 11.1 with a female predominance (55%). In IPF, Definite UIP was identified in 29.3% while probable UIP was identified in 59%. In HP a compatible or typical fibrotic HP pattern was identified in 77.5% and a compatible or typical non fibrotic HP pattern was identified in 12.5%. Baseline forced vital capacity (FVC) was 2.87 ± 3.81 L for IPF compared to 2.37L ± 0.77 for HP with a percent (%) predicted FVC 68.9% ± 16.7 for IPF and 70.4 ± 17.7 for HP. Baseline diffusing lung capacity for carbon monoxide (DLCO) was 12.75 ± 5.94 and 12.66 ± 6 ml/min/mmHg with a % predicted DLCO 51.6% ± 17.9 and 54.7 ± 24.8 for IPF and HP, respectively. Any immunoglobulin laboratory abnormality was present in 48.8% of IPF vs 60% of HP. IgG2 was the most common abnormality in IPF and HP at 22.8% and 34.1%, respectively. An elevation of IgA (OR 2.48,95% CI 1.17-5.26, p<.05) or a decrease of IgM (OR 3.57, 95% CI 1.26-10.1 p<.05) was associated with increased mortality in IPF. IgA was found significantly higher in IPF non survivors versus survivors (366.6 ± 152.4 vs 300.4 ± 150.4, mean difference 66.2, p<.05). In HP no abnormality in immunoglobulin was found statistically significant but in those with any IgA abnormality a trend towards lower disease progression by CT (OR 0.12, 95% CI 0.01-1, p = 0.05) was found. There were no significant differences for other immunoglobulin in lung transplant, disease progression on CT, change of antifibrotic therapy or ILD exacerbation. Conclusions Immunoglobulins may represent a prognostic biomarker in IPF and HP. Research integrating immunoglobulin profiling with clinical phenotypes may provide further understanding of the role of immune dysregulation in IPF and HP.