Determination of CK-MB levels
CK, or creatinine kinase, is an enzyme responsible for the cells’ energy production. There are three isoenzymes (types):
- CK-MM: located in skeletal and cardiac muscle
- CK-BB: mostly present in the brain and smooth muscle (e.g. uterus)
- CK-MB: found mainly in the myocardium, but also in smaller amounts in the skeletal muscle
By determining the level of the CK-MB enzyme, myocardial infarction and other myocardial damage can be diagnosed, and skeletal and myocardial damage can be distinguished, as in case of muscle damage, CK enters the bloodstream from the muscle cells, where CK-MM present in small amounts (BB almost never). As a result, if CK levels are elevated, the CK-MB test helps differentiate whether the increase is caused by heart or skeletal muscle damage. CK-MB typically appears in the bloodstream only when there is damage to the heart muscle in the body.
However, it is worth noting that nowadays, measurement of troponin levels is used more to detect and monitor myocardial damage.
What does the test show?
The test shows the level of the CK-MB enzyme in the blood.
In which cases is it recommended to perform the test?
The measurement of CK-MB levels may be ordered by a physician in case of high CK levels to determine if the increase is due to damage to the skeleton or heart muscle. The doctor might also prescribe the test in the event of suspected heart attack, chest pain, but in case of non-specific symptoms (e.g. shortness of breath, dizziness) as well.
In the case of a heart attack, approx. 3 to 6 hours after the onset of chest pain CK-MB levels rise, peak after half a day, and then fall back to normal levels after two to three days.
What sample is needed for the test?
A blood sample taken from a vein is needed for the test.
What can the result indicate?
Since CK-MB is usually not detected or it is in very small amounts in the blood, elevated CK and CK-MB levels may indicate a myocardial infarction, but any damage to the heart muscle can also cause elevated CK-MB levels or decreased kidney function.
As CK-MB is also present in small amounts in the skeletal muscle, this type of muscle damage can also increase its levels, masking the increase caused by myocardial infraction if both types of damage occur at the same time.
Low CK-MB levels develop when muscle mass is reduced.
What to do after the test?
The test alone cannot diagnose any diseases, and in all cases consult an internist or haematologist to determine the exact diagnosis and required therapy.