Clinical utility of CKMB

CK-MB measurement is an acceptable alternative to cardiac troponin in diagnosis of AMI. CK-2 rises in about 4-6 hours after onset of AMI and peaks at 24 hours. It returns to normal at 48-72 hours. It also has higher sensitivity after 3 hours (100%) and lower sensitivity at 0 hours in diagnosis of AMI. This suggest the traditional serial measurement of sample at 0, 12 and 24 hours might be replaced with four early serum CK-2 measurement at 0, 3, 6, 9 hours after presentation. 

(Source: Arneson's Clinical chemistry, 2nd edition)

 Healthy individual.                                          AMI.

Apart from heart disease CK activity is greatly elevated in all types of muscular disease, during old ages, myositis, etc. Damaged skeletal muscle may contain more CK-MB owing to phenomenon of fetal reversion, thus serum CK-MB isoenzyme may increase in such conditions. Hypothyroid subjects have elevated CK activity. In Duchene type muscular dystrophy value upto 50-100 times URL is seen.

Relative index (CK-MB mass assay/total CK x 100) may be used as an indicator of MI. A relative index >3% is indicative of AMI.