Creatine kinase (CK) - plasma or serum

Last updated: Tuesday, 06, April, 2004

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Item Process
Specimen

5 mL blood in lithium heparin or plain tube.

Method

Spectrophotometry.

Reference Interval

Influenced by gender and method; local laboratory reference intervals should be ascertained. Typically:

Neonate: 70-380 U/L
Adult female: 30-180 U/L 
Adult male: 60-220 U/L.

Application

A sensitive, but not specific, test for the diagnosis and monitoring of myocardial infarction. CKMB with CKMB/CK ratio is more specific, but has been superseded by cardiac troponin T or I.

Levels of CK are increased in diseases affecting skeletal muscle. It can be used to detect carrier status for Duchenne muscular dystrophy, although not all carriers have increased levels.

Interpretation

Elevation of CK with CKMB as >5% percent of CK, indicates a myocardial origin of CK. CK levels may also be increased with skeletal muscle injury (eg, after intramuscular injection or excessive exercise), in myositis, myopathy, rhabdomyolysis or hypothyroidism.

Elevation of no pathological significance  is seen in patients with a 'macro-CK' (a complex of CK with an immunoglobulin).

Isoenzyme studies may be useful in investigating increased CK activities of uncertain cause.

Reference

French JK, White HD. Clinical implications of the new definition of myocardial infarction. Heart. 2004 Jan;90(1):99-106. Review.