Autoantibodies in interstitial lung disease

Abstract

Background: The prevalence and impact of screening for autoantibodies (autoAb) in interstitial lung disease (ILD) patients without a defined connective tissue disease (CTD) is unclear. Aim: Describe the prevalence of CTD autoAb across 5 ILD subgroups. Methods: Consecutive patients referred to Royal Prince Alfred ILD clinic with routine autoAb testing (ANA, ENA, RF, anti-CCP, dsDNA and myositis panel) were included. ANA≥1:320 or any titre if nucleolar/centromere pattern and RF>30IU/mL were considered positive. ILD diagnoses were confirmed at multidisciplinary meeting. Results: 100 ILD patients (mean age 67±13yrs; 54% male; FVC% 75±18; DLCO% 61±16) were included. Diagnoses included idiopathic interstitial pneumonia (IIP, n=48), CTD-ILD (n=14), idiopathic pneumonia with autoimmune features (IPAF, n=8), unclassifiable ILD (n=16) and other (n=14). IPAF and CTD-ILD were younger; IPAF had greater FVC% impairment (62 vs 75%, p=0.04); and CTD-ILD less male predominant (21 vs 73% male, p=0.001) versus IIP. 41% demonstrated ≥1 autoAb (Table 1). ANA was the most prevalent (20%). AutoAb were more common in CTD-ILD overall and highly prevalent in IPAF. 12% demonstrated ENA and myositis Ab, which were more common in IPAF vs IIP (p=0.018; p Conclusion: Autoantibodies are identified across ILD subtypes. Further study is needed to determine their clinical relevance especially in those without a defined CTD. Table 1: AutoAb by ILD subgroup, n (%)