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 ache, stiffness, paralysis, confusion, etc. The results of the creatine phosphokinase test can also be used to diagnose a heart attack and cause chest pain.

Muscle injuries, Muscle disorders, Muscular dystrophy, Rhabdomyolysis

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 ache 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

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

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

Doctors prescribe the CPK test when they suspect a muscle tissue injury. The CPK test also allows the doctors to detect which tissue has been damaged exactly. Sometimes patients may not realise the exact time at which they had a heart attack. The CPK test results allow doctors to make a diagnosis by analysing the timing of the rise and fall in CPK levels.

Your doctor may ask you to repeat your CPK test to re-evaluate the cause behind a rise in the enzyme’s level. If you are in the hospital and your CPK levels are high, your doctor may ask you to retake the creatine phosphokinase test every two to three days to diagnose certain conditions.

The frequency of the CPK test is determined by your specific diagnosis and the decided treatment plan.

What to Expect During the Test

Before the Test

Usually one doesn't need special preparation for an CPK test. However, if you are undergoing this test alongside another one, your healthcare provider may advise you to fast or avoid certain foods. Do consult a doctor before the test for personalised guidance.

During the Test

When undergoing the CPK test, a blood sample will be taken from a vein in your arm. Here's what you can expect during the test:

•  The area where the needle will be inserted will first be cleaned with an antiseptic solution.
•  A tourniquet band will be tied to your arm to make your veins pop out.
• A needle will be inserted into the vein to draw the blood. This process may cause a brief pinch lasting a few seconds.
• The blood will be collected in a vial or small test tube, which will be labeled with your details.

After the Test

Following the blood collection:

• A bandage will be placed over the insertion site to halt bleeding.
• There may be minor bruising, although feeling dizzy is uncommon. You may be advised to rest for a few minutes.
• Contact your healthcare provider if you notice bleeding, pain, or rashes at the puncture site.

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.

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 activities.

The normal values 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.

Depending on the city and the lab, the cost of a CPK test can differ. Generally, the price for a CPK test ranges from INR 189 to INR 549. Here's a breakdown of the average expenses for a CPK test in several key cities in India: