Enzymes are highly specialized complex proteins that facilitate chemical changes in every part of the body. For example, they help break down food so your body can use it effectively, and they help your blood clot. They are present in every organ and cell in your body—your body needs to function properly.
Enzyme markers are blood tests that analyze specific enzyme activity in the body. Certain diseases or conditions that are passed down through your genes can cause these enzymes to stop working or to be less efficient.
Monitoring the rise or fall of enzyme levels can aid in the diagnosis of a variety of conditions. A doctor may specifically order a blood test for enzyme markers, or abnormalities may be discovered during routine blood tests. In some cases, the test may need to be repeated over the course of several days to measure changes over time.
The CPK isoenzyme test measures the creatine phosphokinase (CPK) in the blood. CPK enzymes are found in the heart, brain, and skeletal muscles.
CPK-1 is found mostly in the brain and lungs. Increased levels of CPK-1 can be caused by:
- brain cancer
- brain injury, stroke, or bleeding in the brain
- pulmonary infarction (the death of lung tissue)
- electroconvulsive therapy
CPK-2 levels rise following a heart attack and may also be due to:
- open heart surgery
- inflammation of the heart muscle
- heart injury
- electrical injuries
CPK-3 levels that are high can be a sign of muscle stress or injury due to:
- crush injuries
- muscle damage, dystrophy, or inflammation
- intramuscular injections
- electromyography (nerve and muscle function tests)
- recent surgery
- strenuous exercise
Some heart enzymes slowly make it into your blood if you’ve suffered a heart attack and your heart has been damaged as a result. Patients who present at the emergency room with heart attack symptoms are generally tested for the presence of heart enzymes in the blood.
Elevated liver enzymes may be due to inflammation or damaged liver cells. Usually, elevated liver enzymes are not due to a serious or chronic liver disease, but can be caused by:
- prescription and over-the-counter medications (statins and acetaminophen)
- alcohol consumption
- heart failure or heart attack
- liver disease (such as hepatitis, fatty liver disease, cancer, and cirrhosis)
- celiac disease (a digestive condition)
- viruses (such as cytomegalovirus (CMV) infection, mononucleosis, and Epstein-Barr virus)
- inflammatory diseases (such as dermatomyositis, pancreatitis, and gallbladder inflammation)
- muscular diseases (such as muscular dystrophy or polymyositis)
- hemochromatosis (too much iron in the blood)
- underactive thyroid
- Wilson’s disease (too much copper stored in the body)
The test is a routine blood test and takes place in a laboratory. No fasting or special preparation is required. However, inform your doctor of all prescription and over-the-counter medications and supplements you take.
Your healthcare provider will use a topical antiseptic to clean a small area of your arm, usually the inside of your elbow or the back of your hand. An elastic band will then be wrapped around your upper arm to create pressure and make it easier to access a vein.
A needle will be inserted into your vein and blood will flow into a small vial. You will likely feel the stick of the needle or a stinging sensation. After the vial is filled, the elastic band and the needle will be removed. A bandage will be placed over the puncture site. Drawing the blood should take only a few minutes and the vial will be sent to a lab for analysis.
According to the National Institutes of Health (NIH), isoenzyme testing for specific conditions is about 90 percent accurate (NIH, 2011).
Side Effects/Risks of Blood Test
Your arm may be sore where the needle was inserted and you might have some mild bruising or throbbing briefly.
Most people have no serious or lasting side effects from a blood test. Rare complications include:
- infection (a small risk whenever the skin is broken)
Contact your doctor immediately if you experience any of these symptoms.
Abnormal test results can indicate a variety of problems—from disease to a simple muscle strain—because enzymes are present in every cell of your body. Your doctor will be able to determine a proper course of treatment based on your exact marker levels and the symptoms you are experiencing.