Alternate Names: CK; Creatine kinase; Creatine phosphokinase
How Performed: Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
This test may be repeated over 2 or 3 days for hospitalized people. The pattern of a rise or fall in CPK (or CPK isoenzymes) can be diagnostically significant.
How To Prepare: Adult:
Usually no special preparation is necessary.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:
How It Feels: When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Risks:
- excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Why Performed: When a muscle is damaged, CPK leaks into the bloodstream. Determining which isoenzyme (specific form of CPK) is elevated will help determine which tissue has been damaged.
This test is used to:
Repeated CPK levels may be performed. The pattern and timing of a rise and/or fall in CPK levels can be diagnostically significant, particularly if a heart attack is suspected.
Normal Values: The normal range is 24 to 194 U/ml.
Note: U/ml = units per milliliter
Abnormal Results: Higher than normal total CPK levels may be seen with:
Additional conditions that may give positive test results:
Cost:
Special Considerations: Other tests will need to be conducted to determine the exact location of muscle damage.
Factors that can affect test results include cardiac catheterization, intramuscular injections, trauma to muscles, recent surgery, and vigorous and prolonged exercise.
Drugs that can increase CPK measurements include amphotericin B, ampicillin, some anesthetics, anticoagulants, aspirin, clofibrate, dexamethasone, furosemide, and morphine.
The total CPK test is about 70% accurate because there are many causes of elevated levels. Isoenzyme testing (for individual types of CPK) is about 90% accurate.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
