Alternative Names creatine kinase-isoenzymes, creatine phosphokinase-isoenzymes, CK-isoenzymes
Definition This test measures the levels of the three alternate forms of the enzyme creatine phosphokinase (CPK) in the blood. These alternate forms are known as isoenzymes and are called CPK-1, CPK-2, and CPK-3.
This blood test determines the amounts of CPK-1, CPK-2, and CPK-3 in the bloodstream. These levels can help a doctor to diagnose certain illnesses and conditions.
CPK-1 is found mainly in the brain and lungs
CPK-2 is found mainly in the heart
CPK-3 is found mainly in skeletal muscle
Damage to the brain, lungs, heart or muscle may cause the corresponding isoenzyme to leak into the bloodstream.
How is the test performed? In order to measure the amount of CPK isoenzymes 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 After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test? Normally, no preparation is required for this test.
What do the test results mean? If a disease process is taking place, the total amount of CPK will be high and the individual isoenzyme increases are used to determine what part of the body is responsible for the increase in total CPK. For example, when a heart attack occurs, the total CPK becomes high because of an increase in the CPK-2 and CPK-3 isoenzymes. The normal total CPK level is roughly 35 to 190 units per litre. This can vary for males and females. Normal values for each of the isoenzymes are as follows:
CPK-1: 0% of the total CPK
CPK-2: 0% to 5% of the total CPK
CPK-3: 96% to 100% of the total CPK
Abnormally high levels of CPK-1 may indicate the following:
brain cancer, head injury or bleeding in or around the brain
rhabdomyolysis (widespread muscle destruction, usually due to alcoholism or exercise)
strenuous exercise
Author: Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
