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Blood Test Tracker

Anti-Mitochondrial Antibody (AMA), screen/titer

Antibodies against part of the cell's energy machinery. A positive result is the best-known blood marker for primary biliary cholangitis, a chronic bile duct condition of the liver.

AI-verified against cited sources. Awaiting expert reviewAlso called AMALOINC 5247-2

What it is

Mitochondria are the parts of your cells that make energy. Anti-mitochondrial antibodies (AMA) target enzymes inside them. This test checks whether AMA are in your blood. Many labs report a titer from an immunofluorescence test, such as 1:40 or 1:80. It is the most diluted your blood can be while the antibody still shows up, so a higher second number means more antibody. Other labs report positive or negative from an ELISA.

Why it matters

AMA are found in most people with primary biliary cholangitis (PBC), a long-term condition in which the small bile ducts in the liver are slowly damaged. When liver blood tests point to the bile ducts, a clearly positive AMA is usually enough for clinicians to confirm PBC without a liver biopsy. AMA can also appear in people with normal liver tests, and a low titer is not always a sign of liver disease.

If it’s high

A positive result means AMA were found. This is strongly linked to PBC, but the result is read together with liver blood tests such as ALP. Low-titer results in people with normal liver tests are less specific, and are found in about 1 in 200 people in blood donor and population studies.

Common causes

  • A low titer with normal liver blood tests, seen in about 0.5% of people in population studies, whose meaning is still being studied
  • A non-specific reaction, which is more likely at low titers
  • Primary biliary cholangitis, the main condition linked to AMA
  • Another autoimmune condition, such as systemic sclerosis, where AMA have been reported in some studies

What can help

  • Ask whether your liver blood tests, especially ALP, are normal and how often they should be rechecked
  • Ask whether a second test, such as an anti-M2 ELISA or other PBC-related antibodies, would add information
  • Tell your clinician about itching, unusual tiredness, or yellowing of the skin or eyes

What can affect your result

  • Test method: immunofluorescence depends on the person reading the slide, and ELISA can be more sensitive
  • Titer: low titers are more likely to be non-specific
  • Treatment for PBC can lower the titer, so repeat results can be confusing
  • Liver blood tests: the same AMA result means different things when ALP is normal and when it is raised
  • Immunofluorescence depends on the person reading the slide, and ELISA can be more sensitive, so the same blood can give different results by different methods.
  • Low titers are more likely to be non-specific reactions.
  • Treatment for primary biliary cholangitis can lower the titer.

When to talk to a clinician

A positive AMA result is not urgent by itself. Talk with a clinician about it, especially if you have persistent itching, unusual tiredness, yellowing of the skin or eyes, or raised liver blood tests. If your liver tests are normal, a common approach is to recheck them once a year.

Questions you could ask

  • Does this result matter for any other autoimmune condition I have?
  • What do my liver blood tests, especially ALP, show?
  • Would an anti-M2 ELISA or other antibody tests add information?
  • How often should my liver tests be rechecked?

Questions people ask

Does a positive AMA mean I have a liver disease?

Not always. AMA are strongly linked to primary biliary cholangitis, but the result is read with liver blood tests. A low titer with normal liver tests is found in about 1 in 200 people, and a common approach is to recheck liver tests once a year.

Can I have PBC with a negative AMA?

Yes. AMA are found in roughly 85 to 95 out of 100 people with PBC. Others have different PBC-related antibodies, such as anti-gp210 or anti-sp100, and a few have no autoantibodies and are diagnosed by biopsy.

What does the titer mean?

A titer such as 1:80 means your blood still showed the antibody after being diluted 80 times. A higher number means more antibody was present. For AMA, a UK guideline says the number does not predict how severe the condition is.

Show the science and sources

For clinicians and researchers

AMA target the E2 subunits of the 2-oxo-acid dehydrogenase enzyme complexes in the mitochondrial inner membrane, chiefly the E2 component of the pyruvate dehydrogenase complex (the M2 antigen) (BSG/UK-PBC 2018). Detection is by indirect immunofluorescence on composite tissue substrates, which is operator-dependent but can pick up other specificities, or by ELISA or immunoblot for M2 antigens, which can be more sensitive and less prone to non-specific reactivity from the raised polyclonal IgM of PBC. No clear evidence favors one approach (BSG). A titer above 1:40 for AMA or another PBC-specific autoantibody is the conventional cutoff for a positive result, and the guideline advises care with low-titer AMA because of the danger of false positives in inflammatory conditions such as fatty liver disease (BSG). The same guideline states that AMA positivity in the right context of cholestatic liver tests is usually sufficient to diagnose PBC without biopsy (strong recommendation, high-quality evidence). It also finds no evidence that the AMA concentration above the diagnostic threshold has prognostic meaning, advises against repeating the test once PBC is established, and notes the titer can fall on ursodeoxycholic acid. For AMA with normal liver tests, older cohorts found biliary features of PBC on biopsy in many such people and that the majority went on to develop PBC over long follow-up, though not advanced liver disease, while recent large studies find low-titer AMA in about 0.5% of the population. BSG advises neither biopsy nor treatment in that group, with annual liver tests. Pooled diagnostic accuracy for AMA was 84% sensitivity and 98% specificity in a 2023 meta-analysis of 24 studies, and 84.5% and 97.8% in a 2014 meta-analysis. ARUP quotes 90-95% of people with PBC as AMA-positive. AMA-negative PBC exists. It is identified by PBC-specific ANA (anti-gp210, anti-sp100, nuclear rim, nuclear dot, centromere) or by biopsy (BSG). Titers and cutoffs differ between labs.

LOINC 5247-2 (primary), 20483-4, 17284-1, 14236-4. Specimen: serum.

Sources

  1. The British Society of Gastroenterology/UK-PBC primary biliary cholangitis treatment and management guidelines, Gut (2018)
  2. EASL Clinical Practice Guidelines: The diagnosis and management of patients with primary biliary cholangitis, Journal of Hepatology (2017)
  3. Mitochondrial M2 Antibody, IgG (ELISA) (test 0050065), ARUP Laboratories
  4. Primary Biliary Cholangitis, ARUP Consult
  5. Diagnostic value of anti-mitochondrial antibody in patients with primary biliary cholangitis: A systemic review and meta-analysis, Medicine (Baltimore) (2023)
  6. The accuracy of the anti-mitochondrial antibody and the M2 subtype test for diagnosis of primary biliary cirrhosis: a meta-analysis, Clinical Chemistry and Laboratory Medicine (2014)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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