Clinical significance of autoantibodies to soluble liver antigen in autoimmune hepatitis

Classification of autoimmune hepatitis (AIH) into different subgroups according to autoantibody status has been proposed: type I (ANA/SMA), type II (LKM-1) and type III (anti-SLA). However, whether type III AIH forms a clinically distinct disease entity remains controversial. The aim of this study was to evaluate the subclassification of AIH into ANA/SMA and anti-SLA positive patients with regard to clinical, biochemical and histologic differences. Ninety-seven consecutive patients with a well-documented long-term course of AIH with ANA/SMA and/or anti-SLA autoantibodies were studied. Clinical, biochemical and histological features of patients with ANA/SMA and/or anti-SLA autoantibodies were compared in a secondary analysis of data acquired prospectively. Anti-SLA autoantibodies were found in 21.6% of patients. Anti-SLA-positive patients tended to have lower transaminases (mean: 153 vs. 247 IU/l), gamma-globulins (25 vs. 31%) and bilirubin (1.8 vs. 3.3 mg/dl) in comparison to ANA/SMA positive patients, but there was a large overlap. HLA-type A1 B8 was more frequent in anti-SLA positive patients, while there was no difference in HLA DR3 and DR4 allotype. Response to immunosuppressive therapy was excellent, but relapse occurred frequently. Diagnosis of anti-SLA positive AIH was often delayed (mean: 68 months from first elevation of transaminases) since testing for anti-SLA autoantibodies is currently not generally available. ANA/SMA and anti-SLA positive patients share most clinical, biochemical, histologic and prognostic features. Distinction between type I and type III AIH is therefore clinically not helpful. However, testing for anti-SLA autoantibodies helps in the diagnosis of AIH in many patients who may otherwise be misdiagnosed.