This is a highly specialized, definitive test for autoimmune liver disease. It's the key diagnostic marker for Autoimmune Hepatitis (AIH) Type 2, a condition where the body's immune system attacks its own liver and kidney cells. If your liver enzymes (SGPT/SGOT) are high, but all viral hepatitis tests are negative, this test is the essential next step. A simple blood draw provides the conclusive, specific answer your doctor needs to get to the root of your liver inflammation.