Creatine phosphokinase (CPK) is a complex protein that is typically found in the heart, skeletal muscles and brain. In a healthy individual, these enzymes are contained in the muscle tissue. When these tissues are damaged, the enzymes can leak into the blood stream in large quantities. This means that a blood test for creatine phosphokinase will indicate whether there has been damage to the muscle tissues.
The three different types of CPK differ slightly based on where in the body they are located, and determining which type is leaking into the blood can help pinpoint the source of the injury. CPK-1 is found in the brain and lung tissues, CPK-2 is in the heart, and CPK-3 is located in the skeletal muscles. A high reading of one type of enzyme not only helps to pinpoint the problem but also to rule out other possibilities.
There is always some level of creatine phosphokinase in the bloodstream, but abnormally high levels can be found in patients suffering from a number of conditions. These include the muscular dystrophies, dermatomyositis, polymyositis, inflammation of the heart or pulmonary infarction. High readings can also be seen in patients who have recently had a heart attack, stroke or convulsions or who have suffered a brain injury.
Creatine phosphokinase levels rise and fall in the bloodstream quickly, so multiple tests might be carried out and to determine whether there is a pattern in the patient's test results. Diagnostically, the results can help determine whether the patient has had a heart attack or can help explore other options for the cause of chest pains. Depending on how drastic the increase in enzyme levels are, creatine phosphokinase can also give doctors an idea of how badly a muscle was damaged.
The test for creatine phosphokinase, also known as a CPK test or creatine kinase, is a simple blood test. There is no preparation required, but drugs such as blood thinners, aspirin, furosemide and ampicillin can interfere with the readings, making it important for the patient to notify his or her doctor of any conflicting over-the-counter medications or prescriptions. Alcohol also can interfere with the test results.
It is also possible for higher-than-normal levels of creatine phosphokinase to show up in the bloodstream. Heavy exercise can pump levels of the enzyme into the bloodstream, because vigorous exercise can damage muscle tissue while making it stronger. Any recent surgeries can leave traces of CPK in the blood, as can recent trauma to any muscles.