Which laboratory test is often used to diagnose primary biliary cholangitis?

The diagnosis of primary biliary cholangitis (PBC) is most commonly associated with the presence of anti-mitochondrial antibodies (AMA). This autoimmune condition primarily affects the small bile ducts of the liver, leading to cholestasis and ultimately cirrhosis. The identification of AMA in a patient's serum serves as a key marker for this disease, as these antibodies are found in approximately 95% of patients with PBC.

While liver function tests can indicate liver dysfunction and may show abnormalities typical of cholestatic liver diseases, they are not specific enough to diagnose PBC on their own. Antinuclear antibodies (ANA) can be present in various autoimmune disorders, including PBC, but they are not definitive for this condition. A complete blood count (CBC) is useful for assessing overall health, evaluating for anemia or thrombocytopenia, but it does not provide specific insight into the diagnosis of primary biliary cholangitis.

Therefore, the presence of anti-mitochondrial antibodies is a hallmark of primary biliary cholangitis and serves as a pivotal laboratory test to confirm the diagnosis.