Antinuclear antibody targets in autoimmune hepatitis and drug-induced liver injury: Diagnostic relevance of nucleosome antibodies.

Background & Aims Anti-nuclear antibodies (ANA) are detected in 70-100 % of patients with autoimmune hepatitis (AIH) and in 22-33 % of patients with drug-induced liver injury (DILI). However, little is known about the specific antigens which they bind to. This study aimed to investigate the antigen specificity of ANA in patients with AIH and DILI and to assess the diagnostic value of these antibodies in differentiating between the two diseases. Methods We performed a retrospective, cross-sectional analysis of ANA-positive patients with AIH or DILI treated at a tertiary referral center. ANA patterns were determined by indirect immunofluorescence, followed by antigen-specific characterization using ELISA. Results A total of 81 patients were included (54 AIH, 27 DILI). A homogeneous ANA pattern was more frequently observed in AIH (75.9 %) than in DILI (48.1 %). Among patients with a homogeneous pattern, anti-nucleosome antibodies were present in 51.2 % of AIH patients and 15.4 % of DILI patients, yielding a specificity of 84.6 % (95 % confidence interval (CI) 54.6-98.1) and a sensitivity of 51.2 % (95 % CI: 35.1-67.1). Anti-nucleosome antibodies demonstrated the highest diagnostic accuracy in this subgroup (area under the curve (AUROC): 0.85; 95 % CI: 0.70-1.00), outperforming or equaling Immunoglobulin G (IgG) (AUROC: 0.85; 95 % CI: 0.74, 0.95), anti-F-actin antibodies (AUROC: 0.81; 95 % CI: 0.69, 0.93) and anti-smooth muscle antibodies (SMA) (AUROC: 0.80; 95 % CI: 0.67, 0.92). Conclusions In ANA-positive patients with a homogeneous ANA pattern, anti-nucleosome antibodies provide high diagnostic accuracy in distinguishing AIH from DILI. These findings suggest that anti-nucleosome antibodies may aid in the diagnostic workup of ANA-positive liver injury.