Creatine kinase, creatine kinase-MB (CK-MB)
A CK-MB test may be used as a follow-up test to an elevated 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. If a troponin test is not available, then the CK-MB test is still considered an acceptable substitute.
CK-MB is normally undetectable or very low in the blood.
If CK-MB is elevated and the ratio of CK-MB to total CK (relative index) is more than 2.5–3, it is likely that the heart was damaged. A high CK with a relative index below this value suggests that skeletal muscles were damaged.
Any kind of heart muscle damage can cause an increase in CK and CK-MB, including physical damage from trauma, surgery, inflammation, and decreased oxygen (ischemia). Strenuous exercise may also increase both CK and CK-MB, but usually with a lower relative index.
Kidney failure can cause a high CK-MB level.
- Sample of blood serum
- We perform the test daily