The CPK isoenzymes test measures the different forms of creatine phosphokinase (CPK) in the blood. CPK is an enzyme found mainly in the heart, brain, and skeletal muscle.

See also: Creatine phosphokinase test

This test is done if a CPK test reveals that your total CPK level is elevated. CPK isoenzyme testing can help pinpoint the exact soure of the damaged tissue.

CPK is made of three slightly different substances:

• CPK-1 (also called CPK-BB) is found mostly in the brain and lungs
• CPK-2 (also called CPK-MB) is found mostly in the heart
• CPK-3 (also called CPK-MM) is found mostly in skeletal muscle

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

If you are in the hospital, this test may be repeated over 2 or 3 days. A significant rise or fall in the total CPK or CPK isoenzymes can help your health care provider diagnosis certain conditions.

Usually, no special preparation is necessary.

Tell your doctor about all the medications you are taking. Certain medications can interfere with test results. Drugs that can increase CPK measurements include the following:

• Amphotericin B
• Ampicillin
• Some anesthetics
• Anticoagulants
• Aspirin
• Clofibrate
• Dexamethasone
• Furosemide
• Morphine
• Alcohol
• Cocaine

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.