Sequential measurements of serum creatine kinase cardiac isoenzyme (CK-MB) levels are used in the diagnosis of myocardial infarction. Measurement of CK-MB is particularly useful if the initial determination of troponin is abnormal or if a recurrence of myocardial infarction is suspected.
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 myocardial damage resulting in increased tissue catabolism in the area. This test measures the CK-MB, which is found mainly in the heart muscle, but also in the tongue, diaphragm, and a minimal amount in skeletal muscles.
In patients suspected of having an acute myocardial infarction, the CK-MB test alone may reveal more information than the determination of total creatine kinase concentration, which may initially show no increase. 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
- Increase: Anoxia, burns (electrical, thermal), cancer (lung), carbon monoxide poisoning, cardiomyopathy, 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 failure, Reye's syndrome, rhabdomyolysis, Rocky Mountain spotty fever, surgery (heart, valve replacement), systemic lupus erythematosus, heart injury. Medications: Doxycycline.
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.
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