The small amount of CK that is normally present in the blood comes primarily from skeletal muscles. Any condition that causes muscle damage and/or interferes with muscle energy production or use can cause an increase in CK. For example, inflammation of muscles, called myositis, can increase CK concentrations.
Rhabdomyolysis, a severe breakdown of skeletal muscle tissue that causes muscle pain, tenderness, weakness and swelling, is associated with significantly elevated levels of CK, often 100 times normal. Measurement of CK is used to assess the extent of muscle damage and to monitor its progress.
Measurement of CK is often used as part of the investigation of patients with suspected muscular dystrophy.
Measurement of CK is requested in people who have sustained severe muscle trauma, particularly from crush injuries, burns or electrocution, and are likely to develop rhabdomyolysis.
CK may also be requested in those who develop symptoms or signs of rhabdomyolysis
after being immobile for a long time on a hard surface, for example during an operation or after a stroke, drugs or alcohol
following very severe exercise
after a fit
during a severe infection
while taking certain medicines, for example a statin to lower cholesterol
Rhabdomyolysis is likely if the urine develops a reddish-brown colour and gives a positive dip-stick test for blood. (Myoglobin, a red protein released from damaged muscle, reacts with the dip-stick in the same way as haemoglobin from blood cells.) The excretion of myoglobin by the kidney can potentially cause kidney failure.
Blood concentrations of CK (or its CK-MM isoenzyme) are also requested as a first step in the diagnosis of muscular dystrophy in infants or children who
have difficulty walking
have difficulty standing
have difficulty lifting weights
need help climbing stairs
The test may subsequently be used to screen family members.
A high CK concentration, or a result that goes up from the first to a second or later samples, generally indicates that there has been some recent muscle damage. Serial test results that peak and then begin to drop indicate that new muscle damage has diminished, while increasing and persistent elevations suggest continuing damage.
Total CK is no longer requested in people with chest pain who are suspected of having had a heart attack. It was superseded first by one of its isoenzymes, CK-MB, which is more specific for heart muscle damage, and more recently by cardiac troponin. Troponin is highly specific, is more sensitive than CK-MB and remains raised much longer after a heart attack.
People who have greater muscle mass have higher normal CK levels. For example, a young fit male will have more muscle mass than an elderly female and hence a higher CK concentration. Normal exercise such as running or cycling and drug injections into muscle can increase CK concentrations.
This article was last reviewed on 8 January 2014. | This article was last modified on 28 January 2014.
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