Useful For

Creatine kinase (CK) is a key enzyme of energy metabolism in muscle, catalyzing the reversible physphorylation of creatine.  This dimeric enzyme has two active subunits, M and B, which associate to form three isoenzymes, CK-MM, CK-MB, and CK-BB.  CK-MM is found predominantly in skeletal muscle and CK-BB in brain.  CK-MB is found predominantly in cardiac muscle accounting for approximately 10-40% of myocardial CK.

The low concentration of CK-MB in normal serum and non-cardiac tissues is the basis of its widely accepted use as a diagnostic indicator of myocardial injury.  Damage to the myocardium results in a transient release of CK-MB into the circulation.  This increase in CK-MB reaches a peak in 12 to 24 hours, then returns to normal within 48 to 72 hours. This characteristic temporal pattern is diagnostic for AMI.  Approximately 98% of patients with AMI exhibit elevated serum CK-MB while only 3% of non-AMI patients exhibit abnormal CK-MB.