What is Creatinine Kinase MB/ Creatinine Phosphokinase MB (CK-MB)?
Also Known As:
CK MB CPK MB
Creatine kinase-MB (CK-MB) is a form of an enzyme found primarily in heart muscle cells. This test measures CK-MB in the blood.
CK-MB is one of three forms (isoenzymes) of the enzyme creatine kinase (CK). These isoenzymes include:
- CK-MM (found in skeletal muscles and the heart)
- CK-MB (found mostly in the heart, but small amounts found in skeletal muscles)
- CK-BB (found mostly in the brain and smooth muscle, such as the intestines and uterus)
CK is released from muscle cells and is detectable in the blood whenever there is muscle damage. The small amount of CK that is normally in the blood is primarily CK-MM. CK-BB almost never gets into the blood, and CK-MB will typically only be present in significant amounts when the heart is damaged. A CK test measures the total level but does not distinguish between the three isoenzymes. When there is an increased amount of CK present in the blood, the CK-MB test can be used to determine whether it is due to heart damage or is more likely to be related to skeletal muscle injury.
How is it used?
A creatine kinase-MB (CK-MB) test may be used as a follow-up test to an elevated creatine kinase (CK) in order to determine whether the increase is due to heart damage or skeletal muscle damage. The test is most likely to be ordered if a person has chest pain or if a person’s diagnosis is unclear, such as if a person has nonspecific symptoms like shortness of breath, extreme fatigue, dizziness, or nausea.
CK and CK-MB were once the primary tests ordered to detect and monitor heart attacks, but they have now been largely replaced by the troponin test, which is more specific for damage to the heart.
Sometimes, the CK test may be used if a heart attack is suspected and a troponin test is not available. In this case, when CK is elevated, a CK-MB test may be used as a follow-up test to determine whether the increase is due to heart damage or skeletal muscle damage.