Mitochondrial antibodies are found in a variety of liver diseases and have been characterized to react with at least nine different mitochondrial antigens (M1 " “M9). M2, M1, and M7 are antigens on the inner mitochondrial membranes while the M3, M4, M5, M6, M8, and M9 antigens are present on the outer membranes. Antibodies to the M2, M4, M8, and M9 antigens are found in patients with PBC. About 95% of patients with PBC will be positive for anti-M2. When M4 and M9 are also present, the patient usually has a more rapidly progressive disease course. Some PBC patients (<5%) may only have anti-M9. These patients are usually early in the disease course and may have a more limited disease.
Normal range:
Immunofluorescence assay (IFA): negative, if positive, results are tittered, ELISA: <1:40 titer.
AMA titers >1:40 are significant.
Use
Diagnosis of primary biliary cirrhosis (PBC)
Interpretation
Increased In
Ninety-five percent of PBC cases
Decreased In
NA
Limitations
Quantitative measurements of AMA do not reflect on the progression of the disease.
Five to ten percent of cases of PBC do not have detectable levels of AMA.
Some individuals with host versus graft disease have measurable levels.
Although AMAs serve as highly sensitive markers for the diagnosis of PBC, AMAs can frequently be detected in patients with other diseases, such as primary systemic sclerosis, Sj ƒ ¶gren syndrome, rheumatoid arthritis, and autoimmune hepatitis.
The M2, M4, and M8 staining patterns are indistinguishable by immunofluorescence, so specific EIA assays must be used to determine which of these antibodies are present in a positive serum. Anti-M9 antibodies can only be detected by EIA assay.