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Test ID: AMA    
Mitochondrial Antibodies (M2), Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Establishing the diagnosis of primary biliary cirrhosis

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

Antimitochondrial antibodies (AMAs) are detectable by indirect immunofluorescence in >90% of patients with primary biliary cirrhosis (PBC), but this method also detects AMAs of differing specificities in other diseases. The mitochondrial antigens recognized by AMAs in patients' sera have been classified numerically as M1 through M9, with the M2 antigen complex recognized by AMAs in sera from patients with PBC. M2 antigen is comprised of enzyme proteins of the 2-oxoacid dehydrogenase complex that are located on inner mitochondrial membranes. Included in this group of autoantigens are the pyruvate dehydrogenase complex, and 2-oxoglutarate dehydrogenase complex.

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.

Interpretation Provides information to assist in interpretation of the test results

Positive results for antimitochondrial antibody (AMA) of M2 specificity are highly specific for primary biliary cirrhosis (PBC), and false-negative results are rare.

 

A positive result for AMA of M2 specificity in a patient with clinical features of PBC is virtually diagnostic for this disease.

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

The level of antimitochondrial antibody (AMA) is not useful to indicate the stage or prognosis of the disease or for monitoring the course of disease. Positive results are found (infrequently) in patients with CREST (calcinosis, Raynaud’s phenomenon, esophageal hypomotility, sclerodactyly, and telangiectasia) syndrome, relatives of patients with primary biliary cirrhosis and other autoimmune diseases.

Supportive Data

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

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Rich RR, et al: Infammatory hepatobiliary cirrhosis. In Clinical Immunology Principles and Practice. 3rd edition. Philadelphia, Elsevier, 2008

2. Muratori L, Granito A, Muratori P, et al: Antimitochondrial antibodies and other antibodies in primary biliary cirrhosis: diagnostic and prognostic value. Clin Liver Dis 2008;12:261-276

3. Kaplan MM, Gershwin ME: Primary biliary cirrhosis. N Engl J Med 2005;353(12):1261-1273

4. Van Norstrand MD, Malinchoc M, Lindor KD, et al: Quantitative measurement of autoantibodies to recombinant mitochondrial antigens in patients with primary biliary cirrhosis: relationship to levels of autoantibodies to disease progression. Hepatology 1997;25(1):6-11