Mitochondrial Antibody
Primary biliary cirrhosis (PBC) is an autoimmune disease that causes destruction of intrahepatic bile ducts. PBC is often associated with other autoimmune disorders, particularly Sjogren syndrome. Anti-mitochondrial antibodies (AMA) are found in almost all patients with PBC and are considered the serological hallmark of the disease. AMA are useful diagnostically in distinguishing primary biliary cirrhosis from other types of chronic liver disease. They are present in approximately 95% of patients with primary biliary cirrhosis, but in only 7-30% of patients with chronic active hepatitis and cryptogenic cirrhosis. Patients with extrahepatic biliary obstruction, Wilson's disease, hemochromatosis, and alcoholic cirrhosis rarely have elevated titers. AMA are present in less than 2% of healthy individuals and in less than 5% of patients with SLE, rheumatoid arthritis and other autoimmune diseases.
Traditionally, AMA have been detected with an immunofluorescent assay that looked for a mitochondrial pattern of staining of tissue sections. More recent studies have determined that AMA represent a heterogeneous mixture of antibodies to at least 9 different antigens, which are designated M1 – M9. The most predominant antibody reactivity in the sera of patients with PBC is directed against the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complex (M2 antigen), which is located on the inner mitochondrial membrane.
The level of anti-M2 antibody is not helpful in determining the stage or prognosis of the disease. I also should not be used to monitor the clinical course of disease.
An enzyme immunoassay is now available for specific detection of antibodies against purified M2 antigen. Reference range for the Kallested Anti-mitochondrial antibody kit is:
- Negative: <0.1 Units
- Borderline: 0.1-0.3 Units
- Weakly positive: 0.4-0.9 Units
- Positive: > or =1.0 Units
Specimen requirement will continue to be one red top or SST tube of blood.
Reference
Muratori L, Granito A, Muratori P, et al: Antimitochondrial antibodies and other antibodies in primary biliary cirrhosis: diagnostic and prognostic value. Clin Liver Dis 2008;12:261-276
