Creatine Phosphokinase (CPK) Test Information
Author: Thomas C. Weiss
Contact : Disabled World
Published: 2015-03-17 - (Updated: 2019-01-14)
A creatine phosphokinase test may be used to detect inflammation of muscles or serious muscle damage, or to diagnose rhabdomyolysis.
Creatine phosphokinase or, 'CPK,' is an enzyme found in high concentrations in a person's muscles where it facilitates a person's muscle contraction. CPK is also referred to as, 'creatine kinase,' or, 'CK.' A doctor might check a person's CPK when they are concerned a person has experienced muscle damage or breakdown. In a rare condition called, 'rhabdomyolysis,' extreme muscle breakdown floods a person's blood with CPK and additional chemicals in their muscle cells. Some of these are toxic to a person's kidneys, making the condition a dangerous one. A doctor might repeatedly check a person's CPK levels in people with suspected rhabdomyolysis to assess any potential risks to the person's kidneys.
People who take cholesterol-lowering medications called, 'statins,' at times experience increases in CPK levels as a side-effect of the medication. A person's heart is made of muscle and during a heart attack, CPK leaks out of the person's heart along with other enzymes. A doctor might check CPK repeatedly over a period of time in a person who may be having a heart attack. 'Troponin,' another enzyme present in a person's heart, is often times relied upon more for this purpose than CPK. The level of CPK may be somewhat elevated in a number of people after they exercise, or due to reasons that remain unclear.
The Creatine Phosphokinase (CPK) Test
A creatine phosphokinase (CPK) test might be used to detect inflammation of a person's muscles or serious muscle damage, or to diagnose rhabdomyolysis if the person is experiencing signs and symptoms such as dark urine, muscle aches, or muscle weakness. The person's urine may be dark due to the presence of, 'myoglobin,' a substance released by damaged muscles that may be harmful to the person's kidneys. A CPK test may be ordered by a doctor by itself, or along with additional blood chemistry tests such as creatine, BUN, or electrolyte tests. A urine myoglobin is another test a doctor might order.
A person might have muscle injury with few or non-specific symptoms such as fever, weakness and nausea that may also be seen with a variety of additional conditions. A doctor might use a CPK test to help detect muscle damage in these instances, particularly if a person is taking a statin medication, are using cocaine or ethanol, or has been exposed to a known toxin that has been linked with potential damage. In people who have experienced physical trauma, a CPK test may at times be used in order to evaluate and monitor the person's muscle damage.
A CPK test might also be ordered if a person is experiencing chest pain or other symptoms that lead a doctor to suspect heart damage. The assay was once one of the main tests ordered to help diagnose a heart attack, although in America the use of CPK has been largely replaced by troponin. The CPK test might also at times be used to detect a second heart attack that happens soon after the first one.
A series of CPK tests might be used to monitor muscle damage, to include heart muscle damage, and to find out if it resolves or continues. If a CPK is elevated and the location of the muscle damage is not clear, a doctor might order, 'CK isoenzymes,' or a, 'CK-MB,' as follow-up tests to distinguish between the three types of CPK:
- CK-BB, found mainly in the brain
- CK-MB, found mainly in the heart muscle
- CK-MM, found primarily in skeletal muscle
When a person has one of these types of CPK in their blood it is primarily from the person's smooth muscles, to include the uterus, intestines or placenta. The CPK test might at times be ordered when a person has chest pain and a heart attack is suspected. It may be order after a person has experienced a heart attack and has been diagnosed with one. A doctor might order a CPK test to monitor ongoing heart damage.
When a person's total CPK levels are very high it usually means there has been stress or injury to the affected person's muscle tissue, brain, or their heart. Muscle tissue injury is most likely. When a muscle is damaged, CPK leaks into the person's bloodstream. Figuring out which particular form of CPK is elevated assists a doctor to determine which tissue has been damaged. A CPK test might be used in order to:
- Diagnose a heart attack
- Evaluate the cause of chest pain
- Determine if or how badly a muscle is damaged
- Detect polymyositis, dermatomyositis and additional muscle diseases
- Differentiate between malignant hyperthermia and postoperative infection
The timing and pattern of a rise or fall in a person's CPK levels can be diagnostically significant, especially if a heart attack is suspected. Additional tests, except in unusual instances, are used to diagnose a heart attack.
Understanding CPK Test Results
Average CPK test values are ten to one-hundred and twenty micrograms per liter. The value range might vary somewhat between different laboratories. Some labs use different measurements, or test different samples. Communication with your doctor concerning the meaning of your particular test results is very important. Elevated CPK results may be found in people who have the following:
- Heart attack
- Electric shock
- Delirium tremens
- Lung tissue death
- Muscular dystrophies
- Stroke or brain injury
- Hypo or hyperthyroidism
- Pericarditis after a heart attack
- Dermatomyositis or polymyositis
- Inflammation of the heart muscle
Risks Associated with CPK Test
The risks associated with the CPK test are very low and involve having your blood drawn.
Arteries and veins vary in size from one person to another and from one side of a person's body to the other. Taking a blood sample from some people might be harder than from other people. Additional risks related to having blood drawn are slight, yet may include the following:
- Excessive bleeding
- Fainting or feeling light-headed
Things to Consider Related to the CPK Test
Additional tests should be done to determine the exact location of muscle damage. Factors that might affect a person's test results include:
- Recent surgery
- Heavy exercise
- Trauma to muscles
- Cardiac catheterization
- Intramuscular injections
An elevated CPK result, or one that goes up from the first test to the second one or later samples, usually indicates there has been some recent muscle damage - yet will not indicate its cause or location. Serial CPK test results that peak and then start to drop indicate that new muscle damage has decreased, while increasing and persistent elevations of CPK suggest ongoing damage. People might have CPK levels that are significantly to greatly increased depending on muscle damage severity. People who have rhabdomyolysis may have CPK levels that are as much as one-hundred times average levels.
Increased CPK levels and chest pain indicate it is likely a person has recently experienced a heart attack. Levels that decrease and then increase again may indicate a second heart attack or ongoing damage to the person's heart. Average CPK levels might indicate there has not been muscle damage or that it occurred a number of days before testing. Moderately increased CPK levels might be experienced after strenuous exercise such as contact sports, weight lifting, or extended exercise sessions.
Creatine Phosphokinase (CPK) Information
- The pattern and timing of a rise or fall in CPK levels can be diagnostically significant, particularly if a heart attack is suspected.
- When the total CPK level is very high, it usually means there has been injury or stress to muscle tissue, the heart, or the brain.
- CK can be used in the diagnosis of neuroleptic malignant syndrome, which is manifested as fever, rigidity, altered mental state and autonomic dysfunction.
- In the cells, the "cytosolic" CK enzymes consist of two subunits, which can be either B (brain type) or M (muscle type).
- Lowered CK can be an indication of alcoholic liver disease and rheumatoid arthritis.
- CK is often determined routinely in a medical laboratory. It is also determined specifically in patients with chest pain or if acute renal failure is suspected.
- Cardiac enzyme studies measure the levels of enzymes and proteins that are linked with injury of the heart muscle.
People who experience Kennedy disease, a rare genetic neuromuscular disorder, may also experience elevated CPK levels in their blood. People who have greater muscle mass have higher CPK levels than people who do not. Due to this, men usually tend to have higher levels of CPK in their blood than women. Any kind of muscle damage, to include injections, may temporarily increase CPK levels. A low CPK level might be experienced by women in early pregnancy.
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