Interpretation
Elevated plasma CK activity usually indicates muscle damage. There are 3 isoforms of CK, known as CK-MM (skeletal muscle fraction), CK-MB (myocardial fraction) and CK-BB (brain fraction). The CK assay measures all CK activity in the specimen, regardless of the isoform present.
Conditions that are associated with an elevated CK include:
- Rhabdomyolysis (CK is usually >5,000U/L)
- Myositis
- Muscular dystrophy
- Recent strenous exercise
- Labour
- Cardiac ischaemia (CK-MB fraction will be elevated)
- Hypothyroidism (TSH is usually very high)
- Drugs (e.g. statins)
- Malignant hyperthermia
- Neuroleptic malignant syndrome
- Serotonin syndrome
- Metabolic myopathies (e.g. McArdle disease, Pompe disease, CPT2 deficiency)
- Macro-CK
Macro-CK
Macro-CK is a complex of CK molecules bound together by immunoglobulin that circulates in the plasma. It is biologically inert but is detected by the CK assay as an increase in total enzyme activity. Macro-CK should be suspected in patients with a persistent history of a relatively stable CK rise with no obvious underlying cause. Diagnosis can be confirmed by CK isoenzyme analysis – please discuss with a chemical pathologist if you wish to investigate for macro-CK.
Test Method
Enzymatic spectrophotometry on a Beckman Coulter AU5822 analyser using Beckman Coulter reagents.
