General Practice 2022

CPK exam: what is it for and why is itá high or low

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CPK exam: what is it for and why is itá high or low
CPK exam: what is it for and why is itá high or low

Creatine phosphokinase, known by the acronym CPK or CK, is an enzyme that acts mainly in muscle tissues, brain and heart, and its dosage is requested to investigate possible damage to these organs.

The doctor may request 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.

CPK reference values

The reference values ​​for creatine phosphokinase (CPK) are 32 and 294 U/L for men and 33 to 211 U/L for womenbut may vary depending on the laboratory where the test is performed.

What is the exam for

The creatine phosphokinase (CPK) test is useful to help diagnose diseases such as heart attack, renal or pulmonary failure, among others. This enzyme is subdivided into three types according to where it works:

  • CPK 1 or BB: Found mainly in the lungs and brain;
  • 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 muscle tissue and represents 95% of all creatine phosphokinases (BB and MB).

The dosage of each type of CK is done by different laboratory methods according to their properties and according to the medical indication. When CPK measurement 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 elevated in case of infarction. CK MB levels usually increase 3 to 5 hours after infarction, reach a peak within 24 hours and the value returns to normal between 48 to 72 hours after infarction. Despite being considered a good cardiac marker, the CK MB dosage for the diagnosis of infarction should be done together with troponin, mainly because troponin values ​​return to normal about 10 days after the infarction, being, therefore, more specific.. See what the troponin test is for.

What does high or low CPK mean

Increased concentration of the creatine phosphokinase enzyme may indicate:

High CPK low CPK
CPK BB Infarction, stroke, brain tumor, seizures, lung failure --
CPK MB Heart inflammation, chest injury, electric shock, in case of cardiac defibrillation, heart surgery --
CPK MM Crushing injury, intense physical exercise, long immobilization, use of illicit drugs, inflammation in the body, muscular dystrophy, after electromyography Muscle wasting, cachexia and malnutrition
TOTAL CPK Excessive consumption of alcoholic beverages, due to the use of drugs such as amphotericin B, clofibrate, ethanol, carbenoxolone, halothane and succinylcholine administered together, intoxication with barbiturates --

To perform the CPK dosage, fasting is not mandatory, and may or may not be recommended by the doctor, however it is important to avoid performing strenuous physical exercises 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 test is requested with the aim of diagnosing infarction, it is recommended that the relationship between CPK MB and CPK be evaluated using the following formula: 100% x (CK MB/total CK). If the result of this ratio 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 physician should investigate the cause.

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