Definition of Creatine phosphokinase test:

Creatine phosphokinase (CPK) is an enzyme found mainly in the heart, brain, and skeletal muscle. This article discusses the test to measure the amount of CPK in the blood.

See also: CPK isoenzymes

How the test is performed:

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.

The blood sample is sent to a lab, where the amount of CPK is measured.

This test may be repeated over 2 or 3 days for if you are a patient in the hospital.

How to prepare for the test:

Usually, no special preparation is necessary.

Tell your doctor about any medications you are taking. Drugs that can increase CPK measurements include amphotericin B, certain anesthetics, statins, fibrates, dexamethasone, alcohol, and cocaine.

How the test will feel:

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.

Why the test is performed:

When the total CPK level is very high, it usually means there has been injury or stress to the heart, the brain, or muscle tissue. For example, when a muscle is damaged, CPK leaks into the bloodstream. Determining which specific form of CPK is high helps doctors determine which tissue has been damaged.

This test may be used to:

• Diagnose heart attack
• Evaluate cause of chest pain
• Determine if or how badly a muscle is damaged
• Detect early dermatomyositis and polymyositis
• Tell the difference between malignant hyperthermia and postoperative infection
• Determine if you carry a gene for muscular dystrophy (Duchenne)

The pattern and timing of a rise or fall in CPK levels can be diagnostically significant, particularly if a heart attack is suspected.