The CPK-MB test (creatine phosphokinase-MB), also known as CK-MB test, is a cardiac marker[3] used to assist diagnoses of an acute myocardial infarction, myocardial ischemia, or myocarditis.

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.

However, recently, there have been improvements to the test that involve measuring the ratio of the CK-MB1 and CK-MB2 isoforms.

[citation needed] 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.

An autoimmune reaction creating a complex molecule of CK and IgG should be taken into consideration.