CPK-MB test

The CPK-MB test is a cardiac marker[1] used to assist diagnoses of an acute myocardial infarction. It measures the blood level of CK-MB (creatine kinase myocardial band), the bound combination of two variants (isoenzymes CKM and CKB) of the enzyme phosphocreatine kinase.

CPK-MB test
Kinetics of cardiac markers in myocardial infarction with or without reperfusion treatment.
LOINC49551-5, 51506-4, 2154-3, 13969-1, 32673-6, 38482-6

In some locations, the test has been superseded by the troponin test. However, recently, there have been improvements to the test that involve measuring the ratio of the CK-MB1 and CK-MB2 isoforms.[2]

The newer test detects different isoforms of the B subunit specific to the myocardium whereas the older test detected the presence of cardiac-related isoenzyme dimers.

Many cases of CK-MB levels exceeding the blood level of total CK have been reported, especially in newborns with cardiac malformations, especially ventricular septal defects. This reversal of ratios is in favor of pulmonary emboli or vasculitis. An autoimmune reaction creating a complex molecule of CK and IgG should be taken into consideration.[3]

References
  1. Guzy PM (December 1977). "Creatine phosphokinase-MB (CPK-MB) and the diagnosis of myocardial infarction". West. J. Med. 127 (6): 455–60. PMC 1237914. PMID 339548.
  2. "Use of Cardiac Markers in the Emergency Department: - eMedicine". Retrieved 2009-01-10.
  3. Boucek RJ Jr; Kasselberg AG; Boerth RC; Parrish MD; Graham TP Jr (July 1982). "Myocardial injury in infants with congenital heart disease: evaluation by creatine kinase MB isoenzyme analysis". Am J Cardiol. 50 (1): 129–35. doi:10.1016/0002-9149(82)90018-2. PMID 7090995.
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