From the Guidelines
Mitochondria M2 IgG antibody testing in serum by immunofluorescence should be considered positive at a titer of 1:40 or higher, as this strongly suggests primary biliary cholangitis (PBC) with high specificity, according to the European Association for the Study of the Liver guidelines 1. This test measures the presence and concentration of anti-mitochondrial antibodies that target the M2 antigen complex found in mitochondria. Key points to consider when interpreting the results of this test include:
- A positive result is highly specific for PBC, making it a valuable diagnostic tool when clinical suspicion exists 1.
- Patients with positive results should be evaluated for other signs of PBC, including elevated alkaline phosphatase, gamma-glutamyl transferase, and total bilirubin.
- Additional testing such as liver biopsy may be necessary to confirm the diagnosis in some cases.
- Early detection through this antibody test allows for timely initiation of treatment with ursodeoxycholic acid (UDCA), which can slow disease progression when started early.
- The test may occasionally be positive in other autoimmune conditions, so results should always be interpreted in the context of the patient's complete clinical picture. It's also important to note that the optimal dilution of the revealing fluorochrome-labelled antiserum depends on the original strength of the commercially available antiserum used, usually varying between 1/50–1/100, as stated in the liver autoimmune serology consensus statement from the committee for autoimmune serology of the international autoimmune hepatitis group 1.
From the Research
Mitochondria M2 IgG Ab [Titer] in Serum by Immunofluorescence
- The detection of anti-mitochondrial antibodies, including the M2 subtype, is a key serological hallmark in the diagnosis of primary biliary cholangitis (PBC) 2, 3, 4.
- Immunofluorescence is a sensitive and specific method for detecting M2 anti-mitochondrial antibodies, with a higher specificity compared to enzyme-linked immunosorbent assays (ELISAs) 5.
- The presence of M2 anti-mitochondrial antibodies can be detected years before clinical signs of PBC appear, making early screening and diagnosis possible 2, 4.
- A meta-analysis of 28 studies found that the pooled sensitivity and specificity of M2 anti-mitochondrial antibodies for PBC were 89% and 96%, respectively, with a high diagnostic odds ratio of 169 4.
- A study of 72,173 health check-up individuals found that the presence of M2 anti-mitochondrial antibodies was associated with a increased risk of developing PBC, and that a predictive model based on clinical characteristics and laboratory examinations could identify individuals at high risk of developing the disease 6.
Diagnostic Value of M2 Anti-Mitochondrial Antibodies
- The diagnostic value of M2 anti-mitochondrial antibodies is high, with a sensitivity of 89% and a specificity of 96% for PBC 4.
- The presence of M2 anti-mitochondrial antibodies can be used to facilitate early screening and diagnosis of PBC, and to monitor disease progression 2, 3, 4.
- The use of immunofluorescence for detecting M2 anti-mitochondrial antibodies is recommended due to its high specificity and sensitivity compared to ELISAs 5.
Clinical Implications
- The detection of M2 anti-mitochondrial antibodies is an important tool in the diagnosis and management of PBC 2, 3, 4.
- Early screening and diagnosis of PBC using M2 anti-mitochondrial antibodies can improve patient outcomes and reduce the risk of disease progression 2, 6.
- A predictive model based on clinical characteristics and laboratory examinations can be used to identify individuals at high risk of developing PBC, and to monitor disease progression 6.