AMA - Overview: Mitochondrial Antibodies (M2), Serum (2023)

Useful For

Suggests clinical disorders or settings where the test may be helpful

Establishing the diagnosis of primary biliary cholangitis

This test is not useful for indicating the stage or prognosis of the disease or for monitoring the course of the disease.

Method Name

A short description of the method used to perform the test


NY State Available

Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name

Lists a shorter or abbreviated version of the Published Name for a test

Mitochondrial Ab, M2, S


Lists additional common names for a test, as an aid in searching

AMA (Antimitochondrial Antibodies)

Antibodies to Microtubule Associated Protein 2

Antimitochondrial Antibodies

Immunology Profile (AMA)

Mitochondrial Antibodies, Serum

Primary biliary cirrhosis

Specimen Type

Describes the specimen type validated for testing


Specimen Required

Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-General Request (T239)

-Gastroenterology and Hepatology Client Test Request (T728)

Specimen Minimum Volume

Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.

0.4 mL

Reject Due To

Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus OK
Heat-treated Reject

Specimen Stability Information

Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 21 days
Frozen 21 days

Useful For

Suggests clinical disorders or settings where the test may be helpful

Establishing the diagnosis of primary biliary cholangitis

This test is not useful for indicating the stage or prognosis of the disease or for monitoring the course of the disease.

Clinical Information

Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The presence of antimitochondrial antibodies (AMA) in association with chronic cholestasis after exclusion of known causes of liver disease is strongly suggestive of a diagnosis of primary biliary cholangitis (PBC).(1) AMA have a variable prevalence in other autoimmune diseases such as systemic sclerosis, Sjogren syndrome, autoimmune thyroid disease, rheumatoid arthritis, systemic lupus erythematosus, celiac disease, psoriasis, inflammatory bowel disease, antiphospholipid syndrome, and idiopathic inflammatory myopathy.(2-4) AMA can also be found in some apparently healthy individuals as well as patients with hepatic diseases such as nonalcoholic steatohepatitis and viral hepatitis.(2,3,5)

AMA recognize mitochondrial antigens classified numerically as M1 through M9 with an immunodominance to the M2 antigen in patients with PBC. The M2 antigens comprise of 2-oxo acid dehydrogenase complexes, which are key enzymes in the mitochondrial respiratory chain, namely the pyruvate dehydrogenase complex (PDC), the E3 binding protein of PDC, the 2-oxoglutarate dehydrogenase complex (OADC), and the branched-chain 2-oxo acid dehydrogenase complex.(5) These are multienzyme complexes consist of a minimum of three enzymes, namely E1, E2, and E3, which have a common structure. The identification of the E2 subunit of the PDC (PDC-E2) located on the inner mitochondrial membrane was a major advance in the study of PBC, leading to the development of solid-phase immunoassays such as enzyme-linked immunosorbent assays with recombinant or purified antigens.(6) In PBC patients, AMA are directed against a highly specific epitope within the lipoyl domain of the E2 subunits of the OADC, with the PDC-E2 being the immunodominant mitochondrial antigen.(5,7)

AMA stain the cytoplasm of HEp-2 cells by indirect immunofluorescence assay with a diffuse, granular cytoplasmic pattern. However, this pattern may not be consistent with AMA detected on triple rodent tissue or solid-phase immunoassays, and therefore the sole use of HEp-2 cells for AMA detection is not recommended.(8)

Reference Values

Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative: <0.1 Units

Borderline: 0.1-0.3 Units

Weakly positive: 0.4-0.9 Units

Positive: > or =1.0 Units

Reference values apply to all ages.


Provides information to assist in interpretation of the test results

A positive result for antimitochondrial antibodies of M2 specificity in the setting of chronic cholestasis after exclusion of other causes of liver disease is highly suggestive of primary biliary cholangitis.


Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Positive results are found (infrequently) in patients with CREST (calcinosis, Raynaud phenomenon, esophageal hypomotility, sclerodactyly, and telangiectasia) syndrome, relatives of patients with primary biliary cholangitis, and other autoimmune diseases.

Supportive Data

Testing performed in the Antibody Immunology Laboratory of the antimitochondrial antibody-M2 by EIA revealed a false-positive rate of less than 2% in 196 normal samples, and overall concordance compared with indirect immunofluorescence of 90% on sera from the Mayo primary biliary cholangitis (PBC) Serum Bank. Ten discordant results were obtained (negative by enzyme immunoassay and positive by immunofluorescence assay). Seven of the 10 patients had no histologic evidence of PBC on liver biopsy.

Clinical Reference

Recommendations for in-depth reading of a clinical nature

1. European Association for the Study of the Liver: EASL Clinical Practice Guidelines: The diagnosis and management of patients with primary biliary cholangitis. J Hepatol. 2017 Jul;67(1):145-172. doi: 10.1016/j.jhep.2017.03.0222

2. Colapietro F, Lleo A, Generali E: Antimitochondrial antibodies: From bench to bedside. Clin Rev Allergy Immunol. 2021 Sept:1–12. doi: 10.1007/s12016-021-08904-y

3. Efe C, Torgutalp M, Henriksson I, et al: Extrahepatic autoimmune diseases in primary biliary cholangitis: Prevalence and significance for clinical presentation and disease outcome. J Gastroenterol Hepatol. 2021 Apr;36(4):936-942. doi: 10.1111/jgh.15214

4. Albayda J, Khan A, Casciola-Rosen L, Corse AM, Paik JJ, Christopher-Stine L: Inflammatory myopathy associated with anti-mitochondrial antibodies: A distinct phenotype with cardiac involvement. Semin Arthritis Rheum. 2018 Feb;47(4):552-556. doi: 10.1016/j.semarthrit.2017.06.004

5. Terziroli Beretta-Piccoli B, Mieli-Vergani G, Vergani D: The clinical usage and definition of autoantibodies in immune-mediated liver disease: A comprehensive overview. J Autoimmun. 2018 Dec;95:144-158. doi: 10.1016/j.jaut.2018.10.0046

6. Gershwin ME, Mackay IR, Sturgess A, Coppel RL: Identification and specificity of a cDNA encoding the 70 kd mitochondrial antigen recognized in primary biliary cirrhosis. J Immunol. 1987 May;138(10):3525-3531

7. Leung PS, Choi J, Yang G, Woo E, Kenny TP, Gershwin ME: A contemporary perspective on the molecular characteristics of mitochondrial autoantigens and diagnosis in primary biliary cholangitis. Expert Rev Mol Diagn. 2016 Jun;16(6):697-705. doi: 10.1586/14737159.2016.1164038

8. Vergani D, Alvarez F, Bianchi FB, et al: Liver autoimmune serology: A consensus statement from the committee for autoimmune serology of the International Autoimmune Hepatitis Group. J Hepatol. 2004 Oct;41(4):677-683. doi: 10.1016/j.jhep.2004.08.002

Method Description

Describes how the test is performed and provides a method-specific reference

A recombinant pyruvate dehydrogenase complex -E2 (M2) antigen for detection of antibodies against M2 is attached to the surface of a microplate. Diluted patient serum, standards, or controls are added to the wells, and the M2 specific IgG and IgM antibodies, if present, bind to the antigen. All unbound human antibodies are washed away, and a conjugate of enzyme-labeled polyclonal antibody to human IgG and IgM is added. The enzyme conjugate binds to the antibody complex. Excess enzyme-conjugate is washed away, and substrate is added. After a specified time, the enzyme reaction is stopped. The intensity of the color generated is proportional to the amount of anti-M2 IgG and/or IgM antibody in the sample. The results are read by a spectrophotometer producing a direct measurement of the anti-M2 IgG and IgM antibodies in the serum. Testing is performed on the Agility instrument by Dynex.(Package insert: Kallestad Anti-Mitochondrial Kit. Bio-Rad Laboratories, Inc; 04/2014)

PDF Report

Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed

Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Saturday

Report Available

The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 3 days

Specimen Retention Time

Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location

Indicates the location of the laboratory that performs the test



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Test Classification

Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information

Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
AMA Mitochondrial Ab, M2, S 51715-1
Result Id Test Result Name Result LOINC Value

Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.

AMA Mitochondrial Ab, M2, S 51715-1


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