The clinical usage and definition of autoantibodies in immune-mediated liver disease: A comprehensive overview.

Autoimmune serology is key to the diagnosis and management of autoimmune liver diseases. Its correct use in clinical practice requires a basic knowledge of the laboratory techniques used for autoantibody detection. Indirect immunofluorescence (IIF) on triple rodent tissue is still the gold standard screening procedure for liver-relevant autoantibodies, while HEp2 cells and human ethanol-fixed neutrophils are used as substrates to characterize nuclear reactivities and to detect anti-neutrophil cytoplasm antibody, respectively. Assays based on purified or recombinant antigens are increasingly used, having the main advantage of being observer-independent and the disadvantage of detecting only autoantibodies whose antigenic target has been identified. The AIH-specific anti-soluble liver antigen antibody cannot be detected by IIF and a molecular-based assay should be used at the screening level. Since autoantibodies may be present in the context of viral hepatitides and other inflammatory liver diseases it is important to exclude these conditions before diagnosing autoimmune liver disease. Anti-nuclear antibody (ANA), most often with a homogeneous IIF pattern on HEp2 cells, characterizes type 1 autoimmune hepatitis (AIH), and is found in association with anti-smooth muscle antibody in about half of the cases. Two IIF ANA patterns are specific for primary biliary cholangitis, namely the rim-like/membranous pattern, and the multiple nuclear dots pattern. Anti-liver kidney microsomal antibody type 1 is the serological hallmark of type 2 AIH, often in association with anti-liver cytosol type 1 antibody. Atypical perinuclear anti-neutrophil antibody, referred to as perinuclear anti-neutrophil nuclear antibody, is frequently detected in primary sclerosing cholangitis, in AIH type 1 and in inflammatory bowel diseases. The anti-asiaglycoprotein receptor antibody is liver-specific but not disease-specific, and reliable commercial assays for its detection are lacking. Anti-mitochondrial antibody is the hallmark of primary biliary cholangitis (PBC), being disease-specific and present in about 95% of the PBC patients. Its incidental detection presages the future development of PBC.