Summary
The relationship has been studied between changes in clotting factors and the onset
of platelet clumping and fibrin formation during the clotting of normal and pathological
blood. In normal blood, glass activation factor activity, factor IX activity and platelet
adhesiveness were found to increase prior to the onset of platelet clumping. There
was no change in factor VIII or factor V activity until after the onset of platelet
clumping. At about this point, detectable thrombin formation occurred and this was
shortly followed by the onset of macroscopic fibrin formation. After fibrin formation,
there was an increase in factor VII activity and a fall in factor IX activity. This
fall in factor IX activity did not occur during the clotting of platelet poor normal
plasma.
During the clotting of haemophilia A blood, there were similar changes to those seen
with normal blood, except that the time of onset of platelet clumping was greatly
delayed and the degree of change was often much less. When haemophilia B blood clotted,
there was a temporary increase in factor IX activity at the point of platelet clumping
which was closely followed by a marked decrease in factor IX activity. This decrease
in factor IX activity was not found during the clotting of platelet poor haemophilia
B plasma. Another difference was that factor VII activity decreased following the
onset of fibrin formation.
In PTA blood the major difference from normal appeared to be a delayed activation
of factor IX.
