Antimitochondrial Ab

This test measures whether antimitochondrial antibodies (AMA) are present in the blood. Moderate or high levels of AMA are strongly associated with primary biliary cirrhosis (PBC). PBC is an autoimmune disorder that causes inflammation and scarring of the bile ducts inside the liver, causing continual liver damage and blockage of the bile flow. It is found most frequently in women between the ages of 35 and 60. More than 90% of those affected by PBC will have high levels of antimitochondrial antibodies.

Increased AMA levels are seen much less often in autoimmune hepatitis, sclerosing cholangitis, liver disease due to chronic inflammatory bowel disease, and bile duct obstruction.

There are nine types of AMA (M1 – M9) of which M2 and M9 are the most clinically valuable. Antibodes to M2 target the pyruvate dehydrogenase (PDC) complex. The presence of the M2 type has been particularly evident in primary biliary cirrhosis, while the other AMA types may be found in other conditions and are not indicative of PBC.

In some laboratories, if testing for AMA is positive, then further tests for the M2 subtype is performed. Some laboratories have started to offer the AMA-M2 test instead of the AMA, which reduces the number of false positives from non-M2 antibodies.

How is the sample collected for testing?

A blood sample is taken by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.