Anti-mitochondrial antibody (AMA)
The signature blood test for primary biliary cholangitis, an autoimmune liver disease. AMA is positive in most people with the condition, so a positive result alongside a cholestatic pattern of raised liver enzymes strongly supports the diagnosis.
What it measures
Anti-mitochondrial antibody (AMA) is an autoantibody directed against components of mitochondria — the energy-producing structures inside cells. Its clinical value is almost entirely as the hallmark test for primary biliary cholangitis (PBC), a chronic autoimmune disease in which the small bile ducts within the liver are slowly attacked and damaged, causing bile to back up (cholestasis) and, over years, scarring. AMA (particularly the M2 subtype) is found in around 90–95% of people with PBC, making it one of the most specific and useful autoantibody tests in medicine: a positive AMA in someone with a cholestatic pattern of liver enzymes — a raised alkaline phosphatase and GGT — is often enough to diagnose PBC without a liver biopsy. Because PBC is far more common in women and often causes few early symptoms (sometimes just tiredness and itching), AMA is frequently the finding that explains an unexpectedly raised alkaline phosphatase. It is read together with the liver enzymes and often IgM, which is characteristically raised in PBC. A small number of people are AMA-negative but still have PBC, so a negative result does not fully exclude it.
What a high value can mean
- Primary biliary cholangitis (PBC) — by far the main association; a positive AMA with a cholestatic liver pattern strongly supports the diagnosis.
- A positive AMA before symptoms — can precede the disease, marking people to monitor.
- Occasionally seen at low levels in other autoimmune or liver conditions — which is why it is read with the liver enzymes.
What a low value can mean
- Negative — the expected, normal result; makes PBC much less likely.
- AMA-negative PBC — a minority of people have PBC despite a negative AMA, diagnosed with other antibodies or a biopsy.
When to discuss with a doctor
AMA is usually requested when liver blood tests show a cholestatic pattern — a raised alkaline phosphatase and GGT — or to investigate unexplained tiredness and itching, particularly in a woman in middle age. A positive AMA in that setting strongly supports primary biliary cholangitis and leads to specialist assessment, because early treatment (usually with a bile-acid medication) protects the liver and greatly improves the long-term outlook. Because a small number of people have PBC with a negative AMA, a strongly cholestatic picture is still investigated even if AMA is negative. Mediora.AI shows AMA alongside alkaline phosphatase, GGT and IgM so the primary biliary cholangitis pattern is visible; the diagnosis and treatment belong with your doctor and a liver specialist.