Creatine Phosphokinase Total (CPK) Test

Creatine phosphokinase (CPK) is an enzyme present in your bloodstream. Enzymes are molecular compounds that influence and regulate vital biochemical processes and reactions in your body. Several vital processes of your body are under the influence of enzymes that regulate different steps of important biological cycles. Creatine phosphokinase is an essential enzyme that influences your muscle functions.

Creatine kinase (CK) helps in the reaction between other compounds that form phosphocreatine, a chemical molecule. This molecule is used to supply cells and tissues with ATP, the main source of energy at the cellular level. This process supplies energy to vital parts of our body, including the heart, brain and skeletal muscles.

Usually, CPK exists in skeletal muscles, heart tissue and brain, etc. In the case of a muscular injury, creatine phosphokinase leaks into the bloodstream. The presence of CPK in the bloodstream is an indicator of muscular damage. The CPK enzyme has different variants; one of them is CK-MB.

CK-MB is a specific indicator of myocardial muscle damage and is one of the most reliable markers of acute myocardial infarction (heart attack). Doctors prescribe the CPK test if a patient has complaints of muscle aches, stiffness, paralysis, confusion, etc. The results of the creatine phosphokinase test can also be used to diagnose a heart attack and cause chest pain.

Other Names of Creatine PhosphokinaseTest

• CPK Test
• Creatinine Test
• Creatine Phosphokinase Test
• Creatine Kinase Test
• Total CK Test

What does the test measure and who is it prescribed to?

The creatine phosphokinase test measures the level of CPK enzyme in the blood. A muscle injury or muscle disorder is suspected when a doctor orders a CPK test. These are the symptoms under which a creatine phosphokinase test is ordered:

• Loss of vision or vision changes
• Slurred speech
• Chest pain or pressure
• Confusion
• Loss of consciousness
• Muscle aches and pain
• Muscle stiffness
• Paralysis
• A feeling of numbness or weakness in one side of the body
• Dizziness
• Difficulty in breathing
• Profuse sweating
• Extreme weakness
• Increased heart rate
• Nausea, indigestion or vomiting
• Cold sweat
• Trouble swallowing
• Stiff or loose joints
• Pain that radiates to your arm or the jaw
• Difficulty in walking or running
• Unusual walking style
• Dark urine

Some conditions for which a creatine phosphokinase test can be prescribed are:

• Heart attack
• Evaluate the cause of chest pain
• Determine which muscle is injured
• Evaluate the severity of muscle damage

Your doctor can prescribe you a creatine phosphokinase test if they suspect muscle disorders such as:

• Rhabdomyolysis: A serious condition due to the death of muscle fibres that leads to the release of their contents into the bloodstream. If rhabdomyolysis is not treated on time, it can lead to kidney failure and more.
• Muscular dystrophy: A group of diseases caused by familial genes that leads to progressive weakness and loss of muscle mass.
• Dermatomyositis: Uncommon inflammatory disease that is marked by muscle weakness and skin rash. It can affect children and adults.
• Polymyositis: A medical condition that causes inflammation of muscles and their blood vessels. It causes muscle weakness and pain.
• Malignant Hyperthermia: A severe reaction to specific drugs that are used for anaesthesia.
• Prolonged seizures
• Hormone disorders like thyroid

The creatine phosphokinase test results are evaluated through a blood sample and analysing the levels of the CPK enzymes present in the blood.

Test preparation

The creatine phosphokinase test is a relatively simple blood test. A healthcare provider will use an antiseptic swab to clean a tiny area of your arm. Your provider will tie an elastic cord around the upper area of your arm. This allows the blood to pool into your veins, making it easier to locate it. The clinician will then draw blood from the inside of your elbow or the back of your hand.

After locating your vein, your provider will insert a needle into the area and aspirate blood into a tube or vial. You may feel a slight sting when the clinician inserts the needle into your arm.

Later, the provider will remove the needle and the elastic band. The clinician will place a small over the puncture wound to prevent the site from bleeding.

The vial will be sent to the laboratory for testing. Your doctor may ask you to repeat the CPK test in some days to see if your enzyme levels have changed. If your CPK levels vary, your doctor will analyze the values and come to a final diagnosis.

Test inclusions: What parameters are included?

The creatine kinase test measures one parameter: the level of the CPK enzyme in the blood. Creatine kinase enzyme is found in the skeletal muscle, heart and brain etc. A trace amount of CK is present in the blood generally that mainly comes from skeletal muscles.

The creatine kinase level increases in blood when there is muscle damage. Any condition or injury that causes muscle injury or prevents the production of muscle energy can lead to an increase in CK. The creatine kinase level can also increase after strenuous exercise and inflammation of muscle (myositis).

CPK can be broken down into three main components.

• CPK-1 is found in the brain and lungs.
• CPK-2 is located in your heart.
• CPK-3 is found in your skeletal muscle.

Muscle injuries, Muscle disorders, Muscular dystrophy, Rhabdomyolysis

In conditions such as rhabdomyolysis, the creatine kinase level can fall between 10,000 to 200,000 or even higher. The higher the result of the CK test, the more are the chances of renal damage and related complications. Low levels of CPK are seen in patients with connective tissue disorders such as systemic lupus erythematosus or rheumatoid arthritis. Low CK levels are also seen in patients with reduced physical activity.

The normal values, parameters, and reference ranges of the test may vary from lab to lab. Please refer to the ranges mentioned in the report and consult a doctor to understand the interpretation of lab reports.

A high CPK test value indicates that there has been recent damage to the muscles. However, the location or cause of the damage is not shown. Subsequent CPK test results may peak and then begin to drop. This indicates that the recent muscle damage has reduced, whereas if the value of your CPK test is constantly elevated, that means there is continued muscle damage.

High CPK value is seen in muscular disorders, which can have several causes. Higher CK levels indicate increased severity of muscle damage. Elevated CPK levels are seen in patients with muscle injuries, burns, trauma, electrocution, etc. A low CK level is sometimes seen in early pregnancy.

The CK test was earlier done to diagnose a heart attack, which was replaced later by another test. Sometimes the creatine phosphokinase test is used to detect a second heart attack that can occur shortly after the first one. Your doctor may order a series of CPK tests to monitor heart damage and evaluate the prognosis of the disorder.

CK levels in the case of heart damage rise within the first few hours. The levels peak between 12 to 24 hours and then return to normal within two to four days. In case of subsequent heart attack or ongoing damage, the CK levels may stay elevated.