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MB fraction of creatine kinase (CK-MB mass) in plasma
Last reviewed: 04.07.2025
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Reference values (norm) of the concentration of KK-MB mass in blood plasma are less than 5 μg/l.
Currently, immunoinhibitory analysis of CK-MB activity is widely used. However, the presence of atypical forms of creatine kinase and adenylate kinase activity (due to erythrocyte hemolysis) in the blood serum may lead to false-positive results. Moreover, CK-MB activity in the blood 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 research method in the early period of myocardial infarction. Instead of measuring CK-MB activity, a two-site immunoenzymometric analysis has recently been actively used, which allows measuring the concentration of the CK-MB mass isoenzyme. The method for determining the concentration of CK-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 CK-MB mass in myocardial infarction in blood plasma occurs earlier (usually in the first 2-4 hours) than the activity of CK-MB and creatine kinase. On average, the interval between the first increase in the concentration of CK-MB mass and the increase in the activity of CK and CK-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. No significant differences in the time of the peak of CK-MB mass values (12-14 hours after an attack of acute pain) and CK-MB activity were found. The level of increase in the concentration of CK-MB mass in plasma during myocardial infarction differs from the norm more strongly than the increase in CK-MB activity in the same patients. The period of increase in the concentration of CK-MB mass in blood plasma during myocardial infarction, which allows a diagnosis to be made using biochemical markers (diagnostic window), is longer for CK-MB mass than for CK-MB activity and averages 69 hours. The concentration of CK-MB mass in blood plasma returns to normal after an average of 70 hours.
The sensitivity and specificity of the method for determining the concentration of KK-MB mass for the diagnosis of myocardial infarction during the first 4 hours from the moment of the pain attack is 49% and 94%, respectively, and after 4-12 hours - 76 and 79%.
Determination of CK-MB mass concentration is a more sensitive test in the diagnosis of non-Q-wave myocardial infarction than CK-MB activity.
An increase in the level of CK-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 for 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 KK-MB mass can be detected in patients with skeletal muscle injuries, after surgeries, hypertensive crisis, and circulatory failure.
To increase the specificity of myocardial infarction diagnostics and reduce false-positive results, when assessing the concentration of KK-MB mass in blood plasma, test system manufacturers recommend using cutoff values, which for KK-MB mass are 7 μg/l. Values above 7 μg/l are more likely to indicate myocardial damage.
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