The determination of creatine kinase isoenzymes is used to detect macro-enzymes (macro-CPK) and to diagnose various pathological conditions of skeletal muscle, in combination with aldolase measurement.
Creatine kinase (or phosphocreatine kinase, CK or CPK) is an enzyme found in the striated and cardiac muscle tissue and in smaller amounts in the brain and reflects tissue catabolism as a result of cellular injury. Creatine kinase catalyzes the metabolism of creatine into creatinine.
The test is performed to detect damage to the myocardium or skeletal muscle or damage to the central nervous system, resulting in increased tissue catabolism in these areas. It is possible to determine the type of tissue that has been damaged (which is the tissue that is subjected to increased catabolism) by performing a screening test for creatine kinase isozymes. This test measures the three types of isoenzymes that make up total creatine kinase: CK-BB, CK-MB, and CK-MM.
- CK-BB (CK1) is found primarily in brain tissue, but also in smooth muscles, the thyroid gland, lungs, and prostate.
- CK-MB (CK2) is found mainly in the heart muscle, but also in the tongue, diaphragm, and a minimal amount in skeletal muscles.
- CK-MM (CK3) is mainly found in skeletal muscles.
In patients suspected of having an acute myocardial infarction, the CK-MB test alone may reveal more information than determining the total creatine kinase concentration, which may initially not be elevated. Measurement of CK-MB at 9 hours after onset of symptoms provides an accurate clinical evaluation in 99% of myocardial infarction cases.
Possible Interpretations of Pathological Values
- Increased CK-BB (Brain): Anoxia, biliary atresia, brain injury, cancer (breast, gastrointestinal, prostate, extended tumors), vascular stroke (bleeding, infarction), dialysis, hypothermia, intestinal necrosis, childbirth, malignant hyperthermia, renal failure, shock, CNS surgery, uremia
- Increased CK-MB (Heart): Anoxia, burns (electrical, thermal), cancer (lung), carbon monoxide poisoning, myocardial infarction, vasculitis, congestive heart failure (rare), coronary angiography (rare), coronary insufficiency (rare), hypothermia, hypothyroidism, malignant hyperthermia, muscular dystrophy (Duchenne), myocardial infarction, myocarditis, severe myoglobinuria, polymyositis, pulmonary embolism, chronic renal insufficiency, Reye's syndrome, rhabdomyolysis, Rocky Mountain spotted fever, surgeries (heart, valve replacement), systemic lupus erythematosus, heart injury. Medications: Doxycycline
- Increased CK-MM (Muscle): Cardiac catheterization (with myocardial injury), coronary angiography (with myocardial injury), hypothyroidism, intramuscular injections, muscle trauma, muscular dystrophy, myocardial infarction, psychosis (acute), Reye's syndrome, shock, surgery, skeletal muscle injuries
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.