Summary
The thrombin generation test is used to study coagulation in patients with haemorrhagic
diseases or with high thrombotic risk. To our knowledge, this is the first study investigating
the relative influence of coagulation factors on thrombin generation in plasma. The
aim was to investigate the influence of coagulant factors, anticoagulant factors,
and tissue factor (TF) on three parameters: endogenous thrombin potential (ETP), peak
thrombin concentration, and lag time for the appearance of thrombin. At a low TF concentration,
all factors except factor XI influenced thrombin generation. At a high TF concentration,
only the factors of the extrinsic pathway exerted an influence. ETP and peak thrombin
were linearly correlated to factor II concentration. Factor V and factor VII effects
increased hyperbolically with factor concentration. The influence of factor X on thrombin
generation depended onTF concentration. In the absence of factorVIII and factor IX,
ETP fell to 60–70% of the normal when peak thrombin fell to 25–30% of the normal.
Fibrinogen concentration influenced ETP and peak thrombin and decreasing fibrinogen
levels shortened the lag time. As expected, decreasing antithrombin concentration
caused dramatic increases in thrombin generation. Protein S prolonged the lag time,
especially at a low TF concentration. No effect of protein C was observed, likely
due to the absence of thrombomodulin. The thrombin generation test was more sensitive
to factor deficiencies at low than at high TF concentration. ETP was not the most
critical parameter for studying coagulation factor deficiencies. Instead, peak thrombin
was the most sensitive parameter.
Keywords
Anticoagulant factor - procoagulant factor - thrombin generation - tissue factor