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CPK isoenzymes

Alternative Names
creatine kinase-isoenzymes, creatine phosphokinase-isoenzymes, CK-isoenzymes

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 After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.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
  • other brain trauma, such as from brain surgery
  • lung damage
  • prolonged seizures
  • stroke
Abnormally high levels of CPK-2 may indicate the following: Abnormally high levels of CPK-3 may indicate the following:
  • heart attack
  • muscle damage
  • intramuscular injections
  • muscular dystrophy
  • myositis, an inflammation in the muscles usually due to infection or immune system disease
  • convulsions
  • recent surgery
  • rhabdomyolysis (widespread muscle destruction, usually due to alcoholism or exercise)
  • strenuous exercise
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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