Influence of autoimmune biomarkers on interstitial lung diseases: A tertiary referral center based case-control study

Background: The benefit of routinely measuring autoimmune biomarkers to evaluate patients with interstitial lung disease (ILD) remains debated outside specific contexts such as connective tissue disease (CTD). This study aimed at evaluating the influence of biomarkers on outcome on patients with ILD in a case-control study at a tertiary referral center. We hypothesized that patients with positive autoimmune biomarkers have increased odds of developing ILD even in the absence of CTD. Methods: We reviewed the medical records of 3573 patients seen at the ILD clinic in Mayo Clinic Rochester between September 2001 and September 2006. We assessed their clinical course through June 25, 2013. We included patients with patterns of ILD most often associated with CTD (n = 1256) while excluding patients with other known causes of ILD. Controls (n = 2317) included cases seen at the ILD clinic without evidence of ILD. Results: We identified 930 (26%) cases of ILD alone, 124 (3%) CTD alone, 326 (9%) ILD combined with CTD, and 2193 (61%) with no ILD or CTD. Positive antinuclear antibodies (ANA), rheumatoid factor and aldolase were associated with ILD. After adjustment for age, gender, race, smoking history and CTD, ANA remained an independent risk factor for ILD (OR 1.70, 95% CI 1.33-2.17). Among patients with ILD, the presence of CTD but not biomarker alone was associated with a better survival. Conclusion: In this study, the presence of positive biomarkers was associated with increased odds of ILD, even in the absence of overt CTD, but was not associated with a better outcome.