Autoantibody status is not associated with change in lung function or survival in patients with idiopathic pulmonary fibrosis.

Introduction: A proportion of patients with idiopathic pulmonary fibrosis (IPF) have autoantibodies directed against intracellular targets. This study aimed to determine the relationship between serologic status, lung function decline and survival.

Methods: IPF patients assessed for antinuclear antibody (ANA) and related antigen-specific serology detected by addressable laser bead immunoassay (ALBIA) were included. Demographics, serial pulmonary function tests and survival were compared between patients with and without autoantibodies. Linear mixed models were used to estimate changes in forced vital capacity (FVC) and diffusion capacity for carbon monoxide (DLCO) over time. Cox-proportional hazards models were used to compare survival, adjusted for a composite score including age, sex and baseline lung function.

Results: Of 61 included patients, the mean baseline age was 70 years (SD = 9), 77% were male, and 87% were Caucasian. Either ANA or antigen-specific serology by ALBIA was positive in 25 (41%) during follow-up. ANA was detected in 23 (38%), and specific autoantibodies by ALBIA in 6 (10%). There was no difference in age, sex, race, smoking status, anti-fibrotic use or baseline FVC or DLCO in patients with and without autoantibodies. There was no association between autoantibody status and survival (HR = 1.18, 95% CI 0.61, 2.29), rate of decline in FVC or DLCO (difference in FVC = 4.2 mL/year, p = 0.82; difference in DLCO = 4.6*10mL/min/mmHg/year, p = 0.20).

Conclusion: These data suggest that autoantibodies are common in IPF and that patients with a subset of autoantibodies, but without features of autoimmunity, demonstrate similar disease behaviour to those without autoantibodies.