This test measures the level of the enzyme creatine phosphokinase, or CPK, in the blood. CPK is an enzyme found in the heart, brain, and skeletal muscle.

Who is a candidate for the test?

When muscle tissue is damaged, CPK can leak into the bloodstream. The test is usually done to see if muscle has been damaged or a heart attack has occurred.

How is the test performed?

To measure the amount of CPK in the blood, a blood sample is taken from a vein on the forearm or 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 fine 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 for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.