Background: Recently, the concept of interstitial pneumonia with autoimmune features (IPAF) was proposed by the American Thoracic Society.¹ The serologic domain of IPAF is composed of antibodies to extractable nuclear antigens, cyclic citrullinated peptide antibody, a high titer of rheumatoid factor, and a high titer of antinuclear antibody. However, the clinical significance of the serologic domain of IPAF has not yet been evaluated in idiopathic pulmonary fibrosis (IPF).

Objectives: To investigate the clinical significance of autoantibody positivity in IPF.

Methods: We retrospectively reviewed the records of 528 patients who met the ATS/ERS/JRS/ALAT diagnostic criteria for IPF at a tertiary hospital from January 2007 through March 2014. Patients treated with pirfenidone or nintedanib, an established IPF treatment regimen, were excluded. All patients were divided into the following 3 groups: autoimmune IPF (n=153), patients with autoantibodies that met the criteria for the IPAF serologic domain; incomplete autoimmune IPF (n=68), patients who did not completely meet the criteria for the IPAF serologic domain; lone IPF (n=307), patients without autoantibodies. Multivariate Cox proportional hazards models with backward elimination were used to investigate the risk factors for mortality.

Results: The 5 year mortality rates were as follows: autoimmune IPF group, 54.9% (n=84, 3.4 years after diagnosis [median; IQR=1.9–5.0]); incomplete autoimmune IPF group, 64.7%; lone IPF group, 58.6% (n=180, 2.9 years after diagnosis [median; IQR=1.6–4.9]). Independent risk factors for mortality on multivariable analysis in the overall IPF patient population included age at diagnosis (adjusted hazard ratio (HR) 1.028, p=0.002), autoimmune IPF (adjusted HR 0.747, p=0.050), baseline SaO₂ in the 6 min walking test (6MWT, adjusted HR 0.973, p=0.012), baseline distance in the 6MWT (adjusted HR 0.998, p=0.001), baseline forced vital capacity (adjusted HR 0.977, p<0.001), and diffusing capacity of the lungs for carbon monoxide (DLCO) (adjusted HR 0.979, p<0.001). In the autoimmune IPF group, use of glucocorticoid (not for management of acute exacerbation, adjusted HR 1.971, p=0.029), use of immunosuppressants (adjusted HR 0.343, p=0.002), baseline distance in 6MWT (adjusted HR 0.998, p=0.032), and baseline DLCO (adjusted HR 0.975, p=0.003) were independent risk factors for mortality on multivariable analysis.

Abstract SAT0602 – Table 1 Risk factors associated with mortality in autoimmune IPF patients

Conclusions: Our results suggest that positive autoimmunity might be a favourable factor for 5 year mortality in IPF patients compared to those without autoimmunity, and the use of immunosuppressants could be associated with improved mortality in autoimmune IPF patients.

Reference:

1. Fischer A, Antoniou KM, Brown KK, Cadranel J, Corte TJ, du Bois RM, et al. An official European Respiratory Society/American Thoracic Society research statement: interstitial pneumonia with autoimmune features. The European respiratory journal 2015;46(4):976–87.

Disclosure of Interest: None declared

DOI: 10.1136/annrheumdis-2018-eular.6020