Creatine Phosphokinase (CPK)
Creatine phosphokinase (CPK) is an enzyme that plays a key role in supplying muscles with energy for contraction by converting creatine to creatine phosphate. CPK is present in skeletal muscles, heart muscle, and brain, and its blood level reflects the condition of these tissues.
Indications for testing:
- Confirmation of myocarditis, myocardial infarction, and ischemic heart disease diagnoses.
- Suspected muscle diseases (myopathies, polymyositis, dermatomyositis).
- Assessment of muscle tissue damage due to injury or physical exertion.
- Suspected tumors and thyroid gland diseases.
Features of CPK-MB (cardiac fraction):
- CPK has several isoforms: MM (skeletal muscles), BB (brain), and MB (heart muscle).
- CPK-MB is a specific and sensitive marker of myocardial damage.
- In myocardial infarction, CPK-MB levels begin to rise 4–8 hours after onset, peak at 1–2 days, and return to normal approximately by day 3.
- CPK-MB testing is important for diagnosing recurrent infarctions when other markers have normalized.
Result interpretation:
- Normal total CPK levels: 24–170 U/L for women, 24–195 U/L for men.
- Elevated CPK levels may indicate muscle damage, myocardial infarction, myocarditis, trauma, intense physical activity, thyroid diseases, and other conditions.
- Very low CPK levels generally have no clinical significance.
Test preparation:
- Blood should be drawn on an empty stomach.
- Avoid stress, physical exertion, and smoking for 30 minutes before blood collection.
- Sample for analysis: venous blood.
Thus, determining the level of creatine phosphokinase and its MB fraction is an important diagnostic tool for assessing muscle and heart tissue damage, diagnosing myocardial infarction, and other diseases.