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.
A blood sample is needed. This may be taken from a vein. The test is called a venipuncture.
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:
This list is not all-inclusive.
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.
This test is done if a CPK test reveals that your total CPK level is elevated. CPK isoenzyme testing can help pinpoint the exact source of the damaged tissue.
CPK is made of three slightly different substances:
Higher-than-normal CPK-1 levels:
Because CPK-1 is found mostly in the brain and lungs, injury to either of these areas can increase CPK-1 levels. Increased CPK-1 levels may be due to:
Higher-than-normal CPK-2 levels:
CPK-2 levels rise 3 - 6 hours after a heart attack. If there is no further heart muscle damage, the level peaks at 12 - 24 hours and returns to normal 12 - 48 hours after tissue death.
Increased CPK-2 levels may also be due to:
Higher-than-normal CPK-3 levels are usually a sign of muscle injury or muscle stress and may be due to:
Factors that can affect test results include cardiac catheterization, intramuscular injections, recent surgery, and vigorous and prolonged exercise or immobilization.
Isoenzyme testing for specific conditions is about 90% accurate.
Creatine phosphokinase - isoenzymes; Creatine kinase - isoenzymes; CK - isoenzymes
Anderson JL. ST segment elevation acute myocardial infarction and complications of myocardial infarction. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 73.
Chinnery PF. Muscle diseases. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 429.
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.
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