This test measures the levels of the enzyme, aspartate aminotransferase (AST), in the blood. Enzymes help drive chemical reactions in the body.

Who is a candidate for the test?

Diseases of the liver can cause liver cells to release this enzyme into the bloodstream. Therefore, this test is usually performed to help diagnose liver disorders. AST can also be released with heart, muscle, and brain disorders. Therefore, this test may be ordered to help diagnose various heart, muscle or brain disorders.

How is the test performed?

A blood sample needs to be taken in order to measure the level of AST. The blood is usually drawn from a vein in the forearm or the hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial. The sample is sent to the lab to be analyzed. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.