MB-fraction of creatine kinase( cc-MB mass) in blood plasma

Reference values ​​of concentration of CC-MB mass in blood plasma - less than 5 μg / l [Bakker A. J. et al., 1994].

Currently, immunoinhibitory analysis of KK-MB activity is widely used. At the same time, the presence of atypical forms of QA and adenylate kinase activity( due to hemolysis of red blood cells) in the 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 of determining the concentration of KK-MB mass is based on the binding of AT with its M-subunit and other AT- with the B-subunit. The sensitivity of the method is 0.2 μg / l.

The pathological increase in the concentration of CC-MB mass with MI in the blood plasma occurs earlier( usually in the first 2-4 hours) than the activity of KK-MB and KK activity. On average, the interval between the first increase in the concentration of CK-MB mass and the increase in activity of CC and KK-MB is 1 hour. The peak of all markers occurs earlier in patients with early reperfusion in cases of MI 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 MI differs more from the norm than the increase in activity of KK-MB in the same patients. The period of increase in concentration of CK-MB mass in blood plasma in MI, which allows diagnosis on biochemical markers( diagnostic window), is longer for CK-MB mass than for KK-MB activity, and averages 69 hours [Mair JMD et al., 1991].The concentration of CC-MB mass in the blood plasma returns to the average on average after 70 hours.

The sensitivity and specificity of the method for determining the concentration of CC-MB mass for diagnosis of MI within the first 4 hours after the onset of pain are 49% and 94%, respectively, and4-12 hours - 76 and 79% [Bakker AJ et al., 1994].

Determination of the concentration of CK-MB mass - a more sensitive test in the diagnosis of MI without a Q-wave than that of the KK-MB.

Increased 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 for ventricular fibrillation( up to73.2 μg / l), reflecting the presence of microinfarctions or disseminated myocardial lesions [Thomas P. et al., 1996].

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 MI and decrease false-positive results, when evaluating the concentration of CK-MB mass in blood plasma, test system manufacturers recommend using clipping values, which for CK-MB mass are 7 μg / l. Values ​​above 7 μg / L are more likely to indicate myocardial damage.