Creatine phosphokinase (CPK) or creatine kinase is a naturally occurring enzyme that is mainly found in the brain, heart, and skeletal muscles. At the cellular level, CPK is helpful in the formation of phosphocreatine, a high energy molecule, from adenosine triphosphate (ATP) and creatine. This phosphocreatine provides cells with instant energy for biological processes. However, the real significance of CPK levels in the blood has to do with muscle degeneration. When muscle cells break down due to damage, their contents, including CPK, flow into the blood. Thus, a test that reveals high CPK levels can be an indicator of muscle damage.
A CPK test can be used to diagnose a heart attack or evaluate the cause of any chest pains. This involves checking the CPK MB type of isoenzyme that is found in heart tissue. Similarly, damage to skeletal muscle can be measured by studying CPK MM levels. CPK levels are also helpful in early determination of certain diseases such as dermatomyosis and muscular dystrophy.
In most cases, no special preparations are required. It is important to share information regarding any medications you may be taking, since certain common drugs can increase CPK levels. If the test is being conducted for skeletal muscle problems, avoid physical activities for a day before the test. Alcohol should also be avoided for a day. Read basic information on creatine kinase test
Blood is typically drawn from a vein in the arm by placing a tourniquet over the upper arm and using a needle to pierce the vein. The procedure is similar to that used to draw blood for donation. The blood sample is separated into a part containing cells and another that does not (serum). CPK levels are measured as units (U) of enzyme activity per liter (L) of serum. Healthy adult individuals normally show a reading in the range of 20 to 200 U/L. This normal range depends on additional factors such as age, race, and sex. Any increase in overall CPK levels is an indicator of damage or stress to the brain, heart, or muscle tissue. Looking at levels of specific types such as CPK BB or CPK MB can help to determine which tissue has been damaged. In addition to overall levels, the timing and pattern of any shifts in CPK levels can also provide significant indications. This is especially useful in cases where a heart attack might be suspected. The test may be repeated in 2-3 days to confirm any diagnosis.