Creatine kinase MB is the quantitation of the specific cardiac protein CKMB that is used in diagnosing myocardial infarction. Elevated values can be often be detected within 3-6 hours following the onset of chest pain. Testing should be performed at appropriate intervals because CKMB concentration peaks within 12-24 hours and generally returns to normal at 24-72 hours. Abnormal CKMB concentrations are often associated with ischemia or necrotic injury to the heart. Other conditions which may give elevated CK-MB values when the diagnosis of myocardial damage is unclear include skeletal muscle trauma, muscular dystrophy, dermatomyositis, Reyes syndrome, rhabdomyolysis, drug overdose, delirium tremens, chronic ethanol poisoning, and myopathic disorders.
(CK-MB/total CK) x 100