The AMA-M2 (Anti-Mitochondrial Antibody M2) IgG test detects specific autoantibodies targeting the M2 component of mitochondria, primarily used to diagnose Primary Biliary Cholangitis (PBC), a chronic autoimmune liver disease, being present in over 90% of PBC patients. This blood test helps differentiate PBC from other liver issues, showing high accuracy for PBC, but can sometimes appear in other autoimmune conditions like autoimmune hepatitis or Sjögren’s syndrome, indicating the body mistakenly attacks its own liver cells (specifically bile ducts)