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Creatine Kinase-MB Test

Last updated Oct. 11, 2015

Approved by: Krish Tangella MD, MBA, FCAP

What are the other Names for this Test? (Equivalent Terms)

  • CPK Isoenzymes Test
  • CK-MB Test
  • Creatine Kinase MB Type Test
  • Creatine Phosphokinase Isoenzymes Test

What is Creatine Kinase-MB Test? (Background Information)

  • Creatine Kinase-MB Test is performed to detect and measure the levels of Creatine Kinase-MB (CK-MB) in blood
  • Creatine kinase (CK) is an enzyme (a type of protein causing specific chemical changes), found mostly in the brain, heart, and muscles. It has three different forms of CK proteins, called isoenzymes. These are CK-MB, CK-BB, and CK-MM
  • CK-MB is mostly found in the muscles of the heart.The CK-MM variety is mostly found in the skeletal or voluntary muscles of the body, and CK-BB variety, found mainly in the brain and the smooth or involuntary muscles of the body
  • CK-MB gets released into blood, when there is damage to the heart muscles. Thus,in individuals with heart-related symptoms, measuring blood CK-MB levels will help the healthcare provider know about any involvement of the heart and/or if any injury to the heart has occurred
  • The Creatine Kinase-MBTest is used sometimes, as a substitute to troponin test to diagnose or monitor a heart attack. The test may also be done in cases when the CK levels are elevated, in order to differentiate between injury of the skeletal muscles or of the heart

What are the Clinical Indications for performing the Creatine Kinase-MB Test?

A healthcare provider may order a Creatine Kinase-MBTest, often along with Total Creatine Kinase Test, if there is suspicion of an injury to the heart, thus pointing to a heart attack. Nowadays, this test is only used as a substitute to troponin test (which is a more specific and accurate test) for diagnosing and monitoring a heart attack.

Signs and symptoms of a heart attack may include:

  • Chest pain
  • Shortness of breath, or difficulty breathing
  • Palpitations
  • Nausea and vomiting
  • Sweating
  • Dizziness, extreme weakness

In case of a heart attack, the CK-MB levels usually rise 3-6 hours after the onset of chest pain. It peaks in 12-24 hours and then returns to a normal value within about 48-72 hours. In case of an ongoing damage to the muscles of the heart, the levels may rise again, or it may remain elevated for longer intervals.

The CK-MB Test may also be ordered to monitor the effectiveness of clot bursting treatment, if administered, after the heart attack. The level usually rises and then falls rapidly, in case the treatment is effective.

How is the Specimen Collected for Creatine Kinase-MB Test?

Sample required: Blood

Process: Insertion of needle into a vein (arm).

Preparation required: None.However, the healthcare provider should be informed about any medications used before the test, since some medications may interfere with the test results.

What is the Significance of the Creatine Kinase-MB Test Result?

  • A standard reference range for Creatine Kinase-MBTestis not available due to different test values in different laboratories. Hence, the value of CK-MB levels are usually compared to total Creatine Kinase (CK) levels
  • In case of damage to the muscles of the heart, the levels of CK-MB are elevated, and the ratio of CK-MB to total CK (relative index) is more than 2.5-3.0. A high Creatine Kinase, but with a relative index below this value suggests that skeletal muscles and not the muscles of the heart were injured.

Increased levels of CK-MB may also be due to:

  • Trauma to the heart
  • Heart surgery
  • Electrical injuries
  • Heart defibrillation
  • Inflammation of the heart (as in myocarditis)
  • Kidney failure

Some other conditions affecting the heart, such as angina, pulmonary embolism, and congestive heart failure, usually does not cause an increase in CK-MB levels.

  • Vigorous exercise will cause an increase in both CK and CK-MB levels, but the relative index will not be higher
  • Alcohol abuse may also increase CK-MB levels

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

Extensive damage to skeletal muscles can also increase the CK-MB levels, due to the presence of small amounts of CK-MB in skeletal muscles. Troponin test is usually ordered in such cases for more specific results.

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?

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References and Information Sources used for the Article:

http://labtestsonline.org/understanding/analytes/ckmb/tab/test (accessed on 05/03/2013)

http://www.nlm.nih.gov/medlineplus/ency/article/003504.htm (accessed on 05/03/2013)

http://www.hearthealthywomen.org/tests-diagnosis/heart-attack-blood-tests/heart-attack-tests.html (accessed on 05/03/2013)

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 21, 2013
Last updated: Oct. 11, 2015