Analysis of the activated partial thromboplastin time test using mathematical modeling.
Activated partial thromboplastin time (APTT) is a laboratory test for the diagnosis of blood coagulation disorders. The test consists of two stages: The first one is the preincubation of a plasma sample with negatively charged materials (kaolin, ellagic acid etc.) to activate factors XII and XI; the second stage begins after the addition of calcium ions that triggers a chain of calcium-dependent enzymatic reactions resulting in fibrinogen clotting. Mathematical modeling was used for the analysis of the APTT test. The process of coagulation was described by a set of coupled differential equations that were solved by the numerical method. It was found that as little as 2.3 x 10(-9) microM of factor XIIa (1/10000 of its plasma concentration) is enough to cause the complete activation of factor XII and prekallikrein (PK) during the first 20 s of the preincubation phase. By the end of this phase, kallikrein (K) is completely inhibited, residual activity of factor XIIa is 54%, and factor XI is activated by 26%. Once a clot is formed, factor II is activated by 4%, factor X by 5%, factor IX by 90%, and factor XI by 39%. Calculated clotting time using protein concentrations found in the blood of healthy people was 40.5 s. The most pronounced prolongation of APTT is caused by a decrease in factor X concentration.
Biological Faculty, Department of Biochemistry, Room 129, Moscow State University, 119899, Moscow, Russia. al.kogan@mtu-net.ru
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AE
Kogan
D V
DV
Kardakov
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MA
Khanin
D001778:Blood Coagulation Disorders / Q000097:blood / Q000175:diagnosis; D001779:Blood Coagulation Factors / Q000378:metabolism; D015956:Factor XIIa / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D008962:Models, Theoretical; D010314:Partial Thromboplastin Time
D001779:Blood Coagulation Factors; D015956:Factor XIIa