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MB-fraction of creatine kinase (CC-MB mass) in blood plasma
Last reviewed: 23.04.2024
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The reference values (norm) of the concentration of CC-MB mass in the blood plasma are less than 5 μg / l.
At present, immunoinhibitory analysis of the activity of KK-MB is widely used. At the same time, the presence of atypical forms of creatine kinase and the activity of adenylate kinase (due to hemolysis of red blood cells) in the blood serum can lead to false positive results. Moreover, the activity of CK-MB in the serum rarely increases in the first 4-8 hours after an attack of chest pain, which leads to a decrease in the diagnostic sensitivity of this method of investigation in the early period of myocardial infarction. Instead of measuring the activity of KK-MB, recently two-site immunoenzymometric analysis is actively used, which makes it possible to measure the concentration of the isoenzyme KK-MB mass. The method for determining the concentration of CC-MB mass is based on the binding of antibodies to its M-subunit and other antibodies - to the B subunit. The sensitivity of the method is 0.2 μg / l.
Pathological increase in the concentration of CC-MB mass in myocardial infarction in the blood plasma occurs earlier (usually in the first 2-4 hours) than the activity of KK-MB and the activity of creatine kinase. On average, the interval between the first increase in the concentration of CK-MB mass and the increase in activity of CK and KK-MB is 1 hour. The peak of all markers occurs earlier in patients with early reperfusion in cases of myocardial infarction with a Q-wave on the ECG. Significant differences in the peak time of the values of CK-MB mass (12-14 hours after the onset of acute pain) and the activity of KK-MB were not detected. The level of increase in concentration of CC-MB mass in plasma with myocardial infarction differs more from the norm than the increase in activity of KK-MB in the same patients. The period of increase in the concentration of CC-MB mass in blood plasma with myocardial infarction, which allows diagnosis on biochemical markers (diagnostic window), is longer for CK-MB mass than for KK-MB activity, and averages 69 hours. The concentration of CK- MB mass in the blood plasma returns to normal after 70 h.
The sensitivity and specificity of the method for determining the concentration of CK-MB mass for diagnosis of myocardial infarction within the first 4 hours after the onset of a pain attack are 49% and 94%, respectively, and after 4-12 hours, 76% and 79%.
Determination of the concentration of KK-MB mass is a more sensitive test in the diagnosis of myocardial infarction without Q-wave than that of KK-MB.
An increase in the level of CC-MB mass in blood plasma can be detected in patients with angina pectoris (7-9.1 μg / l), myocarditis (up to 20.9 μg / l), cardiomyopathy due to direct electropulse therapy in ventricular fibrillation (up to 73 , 2 μg / l), which reflects the presence of microinfarctions or disseminated myocardial lesions.
A false positive increase in the concentration of CC-MB mass can be detected in patients with skeletal muscle injuries, after surgery, hypertensive crisis, and circulatory failure.
To increase the specificity of diagnosis of myocardial infarction and to reduce false positive results, when evaluating the concentration of CC-MB mass in blood plasma, test system manufacturers recommend using cut-off values that for CS-MB mass are 7 μg / l. Values above 7 μg / L are more likely to indicate myocardial damage.
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