Creatine kinase MB isoenzyme - plasma or serum

Last updated: Wednesday, 14, April, 2004

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Item Process
Specimen

5 mL blood in lithium heparin or plain tube.

Method

Immunoassay, electrophoresis, spectrophotometry.

Reference Interval

0-10 U/L; 0-5% of the total CK (enzyme activity)

0-6 mg/L (immunoassay).

Application

This test has been superseded by cardiac troponin T or I for the diagnosis of myocardial infarction.

May be useful for confirming reinfarction.

Interpretation

CKMB elevation takes about four hours to develop after myocardial infarction, and levels usually return to normal within 48 hours.

Elevation of total CK, and CKMB as a percentage of CK, indicates a myocardial origin of CK. If the total CK is <100 U/L, elevation of CKMB (as a percent of CK) is unreliable as an indicator of myocardial infarction.

There is <5% CKMB in skeletal muscle, so although skeletal muscle disease or damage may cause an increase in total CKMB, the level will be <5% of total CK.

Reference

Adams JE et al. Clin Chem 1994; 40(1): 1291-1295.