Creatine kinase isoforms - plasma or serum

Last updated: Tuesday, 23, March, 2004

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Item Process
Specimen

5 mL blood in lithium heparin or plain tube.

Method

Electrophoresis.

Reference Interval

CKMB2  0-1 U/L; CKMB2/CKMB1 ratio: 0-1.5.

Application

For the diagnosis of myocardial infarction this test has been superseded by cardiac troponin T or I.

Interpretation

There are 3 isoforms of CKMM and 2 isoforms of CKMB in plasma. The CKMM3 isoform and the CKMB isoform are present intracellularly and released following myocardial infarction, but they are converted to CKMM1 and CKMB1 isoforms (respectively) after a few hours in plasma. Thus elevation of CKMM3/CKMM1 or CKMB2/CKMB1 ratios indicates recent release of CK and can be used as early, but non-specific, indicators of myocardial infarction.

Reference

Puleo PR et al. N Engl J Med 1994; 331: 561-566.