AMA optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for AMA:
- Optimal 0 – 1:20 titer (0 – 20 U/mL); sufficient 1:20 – 1:40 titer (20 – 24.9 U/mL); out of range below 0 or above 1:40 titer.
Evidence grade: Established clinical threshold. A band edge that corresponds to a recognised diagnostic, risk or treatment threshold from a major clinical guideline or public-health body.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| titer | 0 – 1:20 | 1:20 – 1:40 | below 0 or above 1:40 |
| U/mL | 0 – 20 | 20 – 24.9 | below 0 or above 24.9 |
What the evidence says
One of the few antibodies specific enough to act on. EASL treats a titre of 1:40 with a cholestatic alkaline phosphatase as diagnostic of primary biliary cholangitis without biopsy, and the British guideline counts a titre above 1 in 40 as positive; it can precede abnormal enzymes by years — so read it beside ALP and GGT rather than alone. A titre of 1:40 is shown as acceptable only because the two guidelines differ on whether 1:40 itself counts; 1:80 and above is out of range. The M2 ELISA in U/mL is a different assay from the titre and its band is its own: 20 or less is negative, 20.1 to 24.9 equivocal and 25 or more positive at ARUP and Labcorp. The two do not convert.
Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.
Sources
- The British Society of Gastroenterology/UK-PBC primary biliary cholangitis treatment and management guidelines — Hirschfield GM, Dyson JK, Alexander GJM, et al. — Gut, 2018 · Clinical guidelineAMA above 1 in 40 with cholestatic liver biochemistry and no other explanation is usually sufficient to diagnose PBC; a titre above 1 in 40 is conventionally positive, and low-titre AMA with normal liver tests is seen in about 0.5% of people. Supports ending the acceptable band at 1:40 rather than 1:80. Full text read through the Europe PMC full-text service for PMC6109281.
- Mitochondrial M2 Antibody, IgG (ELISA) — ARUP Laboratories, 2026 · Laboratory / reference-interval source20.0 units or less is negative, 20.1 to 24.9 equivocal, 25.0 or greater positive. Matches Sera's optimal upper edge of 20 and puts the positive cut-off at 25, not 30. Labcorp's M2 test uses the same three bands. Test directory page as opened in October 2026.
- Mitochondrial (M2) Antibody — Labcorp, 2026 · Laboratory / reference-interval sourceNegative 0.0 to 20.0, equivocal 20.1 to 24.9, positive above 24.9. A second laboratory with the same M2 bands as ARUP. Test directory page as opened in October 2026; it does not print the unit.
- EASL Clinical Practice Guidelines: The Diagnosis and Management of Patients with Primary Biliary Cholangitis — European Association for the Study of the Liver, 2017 · Clinical guidelineEstablishes AMA at 1:40 or above, alongside a cholestatic alkaline phosphatase, as sufficient for diagnosing primary biliary cholangitis without biopsy, and records the roughly 90-95% prevalence in the disease. Sera's optimal band stops below that dilution.
What Anti-Mitochondrial Antibody (AMA) measures
An antibody against mitochondrial antigens, overwhelmingly the M2 subtype, and the defining serological marker of primary biliary cholangitis.
Present in around 90 to 95% of primary biliary cholangitis and rare otherwise, which makes a positive result meaningful in a way few antibodies are. Read it against ALP and GGT: a positive AMA with a cholestatic enzyme pattern is close to diagnostic. It can precede abnormal enzymes by years. Sera stores the dilution denominator, so a report reading 1:160 is entered as 160.