What is an Anti-Mitochondrial Antibody (AMA) lab test?

From the Guidelines

An AMA lab test is a blood test used to diagnose primary biliary cholangitis (PBC), which detects antibodies targeting mitochondria in the liver's bile ducts, with a high specificity of 90-95% for PBC, as indicated by studies such as 1 and 1. The AMA test is typically ordered when a patient shows signs of liver dysfunction, such as elevated alkaline phosphatase levels, fatigue, itching, or jaundice. No special preparation is needed before the test, which involves a simple blood draw. Results are usually reported as positive or negative, sometimes with titer levels indicating antibody concentration. A positive result strongly suggests PBC, though additional tests like liver function tests, imaging studies, or liver biopsy may be needed for definitive diagnosis, as suggested by 1. Early detection through AMA testing allows for timely treatment with medications like ursodeoxycholic acid, which can slow disease progression, as noted in 1 and 1. Some key points to consider when interpreting AMA test results include:

• The test's high specificity for PBC, as mentioned in 1
• The importance of considering clinical presentation and other diagnostic tests, such as liver function tests and imaging studies, as discussed in 1
• The potential for false-negative results, particularly in early stages of the disease, as noted in 1
• The role of AMA testing in monitoring disease progression and response to treatment, as suggested by 1 and 1. It is essential to consider the clinical context and other diagnostic findings when interpreting AMA test results, as emphasized by 1 and 1. In patients with chronic intrahepatic cholestasis, testing for serum antimitochondrial antibodies (AMA) is mandatory, as stated in 1. A liver biopsy may still be appropriate in selected patients, particularly those with a negative AMA test, as recommended by 1. Genetic testing for ABCB4, when available, should be considered in patients with a negative AMA test and biopsy findings that might be compatible with PBC or PSC, as suggested by 1. Overall, the AMA test is a valuable tool in the diagnosis and management of PBC, and its results should be interpreted in the context of clinical presentation, other diagnostic tests, and treatment response, as emphasized by 1, 1, and 1.

From the Research

Anti-Mitochondrial Antibody (AMA) Lab Test

• The Anti-Mitochondrial Antibody (AMA) lab test is used to detect the presence of anti-mitochondrial antibodies in a patient's serum, which are specific markers of primary biliary cirrhosis (PBC) 2, 3, 4.
• PBC is a cholestatic autoimmune disease characterized by the progressive destruction of biliary epithelial cells, leading to fibrosis, cirrhosis, and liver failure 2.
• The prevalence of AMA in PBC is more than 90%, and they can precede clinical symptoms by a long time 2, 3, 4.
• AMA are conventionally detected by indirect immunofluorescence (IIF) using rodent liver, kidney, and stomach sections as substrates, but this method lacks specificity and sensitivity 3, 5.
• More sensitive techniques, such as enzyme-linked immunosorbent assays (ELISAs) or SDS-PAGE followed by immunoblotting, can detect AMA in patients who are negative by IIF 3, 5, 6.
• The diagnostic significance of AMA is well established, but their presence is not exclusive to PBC and can be detected in other liver diseases and autoimmune disorders 3, 4.

Detection Methods

• Indirect immunofluorescence (IIF) is a commonly used method for detecting AMA, but it has limitations in terms of specificity and sensitivity 3, 5.
• ELISAs and SDS-PAGE followed by immunoblotting are more sensitive methods for detecting AMA 3, 5, 6.
• New laboratory tools, such as recombinant antigens, are being developed to improve the detection of AMA and other PBC-specific autoantibodies 5, 6.

Clinical Significance

• AMA are highly specific for PBC diagnosis, but their presence is not sufficient to establish a diagnosis on its own 3, 4.
• The presence of AMA can be detected in patients with overlap syndrome, as well as other hepatic diseases, such as NASH and viral hepatitis 3, 4.
• AMA are also associated with autoimmune diseases, such as Sjögren's syndrome, systemic sclerosis, and systemic lupus erythematosus 4.