Creatinophosphokinase, known by the acronym CPK or CK, is an enzyme that acts mainly on muscle tissues, the brain and the heart, and its dosage is requested to investigate possible damage to these organs.
The doctor may order this test when the person arrives at the hospital complaining of chest pain or to check for signs of a stroke or any disease that affects the muscles, for example.
Reference values
The reference values for creatine phosphokinase (CPK) are 32 and 294 U / L for men and 33 to 211 U / L for women but may vary depending on the laboratory where the test is performed.
What is it for
The creatinophosphokinase test (CPK) is useful to help diagnose diseases such as heart attack, kidney or lung failure, among others. This enzyme is divided into three types according to its location:
- CPK 1 or BB: It can be found in the lungs and brain, mainly; CPK 2 or MB: It is found in the heart muscle and therefore can be used as a marker of infarction, for example; CPK 3 or MM: It is present in the tissue muscle and represents 95% of all creatinophosphokinases (BB and MB).
The dosage of each type of CK is done by different laboratory methods according to its properties and according to the medical indication. When CPK dosage is requested to assess infarction, for example, CK MB is measured in addition to other cardiac markers, such as myoglobin and troponin, mainly.
A CK MB value equal to or less than 5 ng / mL is considered normal and its concentration is usually high in the event of a heart attack. The levels of CK MB usually increase 3 to 5 hours after the infarction, reaches a peak within 24 hours and the value returns to normal between 48 to 72 hours after the infarction. Despite being considered a good cardiac marker, the measurement of CK MB for the diagnosis of infarction must be done together with troponin, mainly because the troponin values return to normal about 10 days after the infarction, being, therefore, more specific. See what the troponin test is for.
What high and low CPK mean
Increased concentration of the creatinophosphokinase enzyme may indicate:
| High CPK | Low CPK | |
| CPK BB | Infarction, stroke, brain tumor, seizures, lung failure | - |
| CPK MB | Cardiac inflammation, chest injury, electric shock, in case of cardiac defibrillation, heart surgery | - |
| MM CPK | Crushing injury, intense physical exercise, long immobilization, use of illicit drugs, inflammation in the body, muscular dystrophy, after electromyography | Loss of muscle mass, cachexia and malnutrition |
| TOTAL CPK | Excessive intake of alcoholic beverages, due to the use of medicines such as amphotericin B, clofibrate, ethanol, carbenoxolone, halothane and succinylcholine administered together, poisoning with barbiturates | - |
To perform CPK dosing, fasting is not mandatory, and may or may not be recommended by the doctor, however it is important to avoid performing strenuous physical exercises for at least 2 days before performing the exam, as this enzyme may be elevated after exercise due to its production by the muscles, in addition to the suspension of medications, such as Amphotericin B and Clofibrate, for example, as they can interfere with the test result.
If the exam is requested in order to diagnose infarction, it is recommended that the relationship between CPK MB and CPK be evaluated using the following formula: 100% x (CK MB / CK total). If the result of this relationship is greater than 6%, it is indicative of cardiac muscle injuries, but if it is less than 6%, it is a sign of skeletal muscle injuries, and the doctor should investigate the cause.
