Creatine phosphokinase (total CPK)
Why this test?
- To confirm the diagnosis of «myocardial infarction», «myocarditis», «myocardiodystrophy».
- To confirm the diagnosis of «polymyositis», «dermatomyositis», «myodystrophy».
- To check for thyroid disease.
- To verify the presence of a tumor process and assess its severity.
- To assess the severity of the course of polymyositis, dermatomyositis, myodystrophy, myopathy.
- To detect the carrier of the Duchenne myopathy gene.
- For diagnosis and assessment of the severity of damage to the heart and muscular system in case of intoxication due to infection, as well as in case of poisoning (carbon monoxide, snake venom, drugs).
In what cases is it prescribed?
- With symptoms of coronary heart disease.
- With symptoms of myocardial infarction, in particular with a vague clinical picture, especially with repeated infarction, atypical localization, pain syndrome or ECG signs, difficulty in differential diagnosis with other forms of coronary heart disease.
- With hypothyroidism.
- With symptoms of myositis, myodystrophy, myopathy.
- When planning a pregnancy by a woman with a family history of Duchenne myopathy.
- In diseases that can lead to damage to the heart or the muscular system.
Creatine kinase is an enzyme that catalyzes the reaction of transferring a phosphoryl residue from ATP to creatine with the formation of creatine phosphate and ADP. ATP (adenosine triphosphate) is a molecule that is a source of energy in the biochemical reactions of the human body. The reaction catalyzed by creatine kinase provides energy for muscle contractions.
Distinguish between creatine kinase, which is contained in mitochondria and cytoplasm of cells. The creatine kinase molecule consists of two parts, which can be represented by one of two subunits.
Thus, in the human body, creatine kinase exists in the form of three isomers: MM, MV, BB.
The MM-isomer is found in skeletal muscles and myocardium, MB - mainly in the myocardium, BB - in the tissues of the brain, in small quantities in any cells of the body. In the blood of a healthy person, creatine kinase is present in small amounts, mainly in the form of the MM isomer. Creatine kinase activity depends on age, sex, race, muscle mass and physical activity.
Creatine kinase enters the bloodstream in large quantities when cells are damaged. At the same time, by increasing the activity of certain isomers, it is possible to draw a conclusion about which tissue is affected: MM-fraction - muscle damage and, to a lesser extent, heart damage, MV-fraction - myocardial damage, BB-fraction - oncological diseases.
Usually tests are performed for total creatine kinase and its MV fractions. Thus, an increase in creatine kinase in the blood allows us to draw a conclusion about tumor processes, damage to the heart or muscles, which in turn can develop as a result of primary damage to these organs (in case of ischemia, inflammation, injuries, dystrophic processes), and as a result of their damage in other conditions (due to poisoning, metabolic disorders, intoxication).
Heart diseases in which cells are destroyed are myocardial infarction, myocarditis, myocardial dystrophy, and toxic damage to the myocardium. Analysis of creatine kinase is of the greatest importance for the diagnosis of myocardial infarction, since the activity of this enzyme increases earlier than others, already 2-4 hours after a heart attack, and reaches a maximum after 1-2 days, then normalizes.
The sooner treatment for a heart attack is started, the better for the patient, which is why timely and accurate diagnosis is so important. Muscle diseases in which cells are destroyed are myositis, myodystrophies, injuries, especially during compression, bedsores, tumors, intensive muscle work, including convulsions. In addition, there is an inverse relationship between the level of thyroid hormones and creatine kinase: when T3 and T4 decrease, the activity of creatine kinase increases and vice versa.