Autoimmune hepatitis (AIH) is a chronic, progressive, heterogeneous inflammatory liver disease of unknown etiology. Diagnosis is often difficult since there is no single diagnostic test for AIH and presenting symptoms can be quite varied. Diagnosis includes evaluation of clinical laboratory and histological findings as well as the exclusion of other causes of chronic hepatitis. Diagnosis is particularly difficult with patients classified with cryptogenic hepatitis, described as having an undefined chronic hepatitis without antibodies to viral or the conventional profile of autoimmune markers. Early diagnosis of AIH and immunosuppressive treatment are essential to help prevent severe liver damage.
AIH patients are generally divided into two groups based on the presence of specific autoantibodies. AIH type 1 (also referred to as classic, active chronic, lupoid, plasma cell, or autoimmune chronic active hepatitis) is the more common type of AIH. AIH-1 is characterized by antinuclear, antismooth muscle (directed against both antiactin and nonactin components), and perinuclear and antineutrophil cytoplasmic antibodies. Liver/kidney microsome antibodies and antiliver cytosol antigen (LC-1) characterize AIH type 2.
Autoantibodies against soluble liver antigen (anti-SLA) show a high specificity (approximately 99%) for AIH; however, they are detectable in only 10% to 30% of patients with AIH. SLA is a 50 kilodalton cytosolic protein that is thought to be involved in the selenocysteine pathway. Anti-SLA and the independently described anti-LP are identical. The findings of anti-SLA has been associated with an increased prevalence of the HLA-DR3 genotype and a decreased prevalence of the HLA-DR4 genotype. Anti-SLA positive patients have a higher rate of relapse after corticosteroid than seronegative patients. Recent studies have suggested that patients with anti-SLA/LP have a more severe course of autoimmune hepatitis, although the exact function and role of this autoantibody remain unclear.
Negative: 0.0−20.0 units
Equivocal: 20.1−24.9 units