Laboratory tests for diagnosis of autoimmune diseases.

1. Antimitochondrial antibody titers of 1:160 are practically diagnostic of primary biliary cirrhosis [71]. Serum antimitochondrial antibody titers of less than 1:16 are seen in 10% of cases of primary biliary cirrhosis. The antimitochondrial antibodies are usually absent in jaundiced patients with extrahepatic obstruction, drug sensitivity, and viral hepatitis. 2. Anti-smooth-muscle antibodies are noted in the various autoimmune liver disorders, viral hepatitis, infectious mononucleosis, malignancy, and intrinsic bronchial asthma. The smooth muscle antibody test helps in the differential diagnosis of lupoid hepatitis vs. systemic lupus erythematosus. The anti-smooth-muscle antibodies are usually absent in systemic lupus erythematosus. 3. The antinuclear antibody is frequently positive in the autoimmune liver diseases. In cases of chronic aggressive hepatitis associated with a high titer of antinuclear antibody the prognosis is usually grave. 4. The presence of antimicrosomal liver and kidney antibody is indicative of chronic aggressive liver disease, which is different from the classic lupoid hepatitis [95, 97]. 5. Hepatitis-B-antigen assay should be performed routinely to exclude viral hepatitis, type B. Heterophile antibody tests should done when the possibility of infectious mononucleosis must be considered. 6. Serum immunoglobulin determinations are of secondary importance in the laboratory diagnosis of autoimmune liver disorders. There is usually a polyclonal elevation of the major immunoglobulin in most chronic parenchymal liver diseases[48].