Creatine Kinase MB/Creatine Kinase Ratio
Does this test have other names?
Ratio of CK-MB to total CK, cardiac index
What is this test?
This test measures the amount of creatine kinase (CK), an enzyme, in your blood. It
also measures a certain isoenzyme of CK called CK-MB. This is found mostly in the
Your body makes 3 forms of CK, including CK-MB. CK is found in the heart, muscles,
and other organs including the small intestine, brain, and uterus. If you have a heart
attack, injured heart muscle cells release CK-MB into your blood.
Because many tissues contain CK, high levels of CK can be a sign of a variety of problems.
Higher CK-MB may point more specifically to heart damage.
Each year millions of Americans visit the emergency room with chest pain, but only
a fraction of those people are actually having a heart attack or another serious,
sudden heart problem. This test helps your healthcare provider figure out whether
you're having a heart attack.
Measuring the ratio of CK-MB to total CK can provide information about the cause of
Why do I need this test?
You may have this test if your doctor suspects you are having a heart attack. Symptoms
of a heart attack often include:
Pain or discomfort in the chest, such as a squeezing sensation or feeling of fullness
Pain in the neck, back, left arm, or jaw
Shortness of breath
Lightheadedness or dizziness
Nausea or vomiting
What other tests might I have along with this test?
Your healthcare provider may also order a test to measure cardiac troponin, or CTn.
This test is more commonly used than CK-MB because it more specifically shows heart
damage. The cardiac troponin level is the considered the best way to detect heart
attack because it is more sensitive and more specific than CK-MB markers.
Your provider may also order an electrocardiogram, or ECG, to measure electrical activity
in your heart and help diagnose a heart attack.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Levels of CK-MB do not rise in your blood within the first 4 to 6 hours after a heart
attack. You may need to have repeated tests to see if you've had a heart attack.
If you've had a heart attack, both CK-MB and the ratio of CK-MB to total CK will rise.
The higher the ratio of CK-MB to CK, the more likely it is that you have a heart problem.
Higher levels of CK-MB may also be caused by muscle damage elsewhere in your body,
by diseases that affect your muscles, and by trauma to your chest.
This test may not be helpful if you have both heart and other muscle damage at the
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Timing is important. If you have the test too soon after a heart attack, your results
may not be accurate.
Strenuous exercise and cocaine use can also affect your results.
How do I get ready for this test?
You don't need to prepare for this test. But be sure your healthcare provider knows
about all medicines, herbs, vitamins, and supplements you are taking. This includes
medicines that don't need a prescription and any illicit drugs you may use.