summary
Normal haemostasis is maintained by a controlled balance between coagulation and fibrinolysis,
involving thrombin and plasmin the respective key enzymes. Simultaneous evaluation
of both enzymes facilitates, therefore, an overall understanding of normal and pathological
haemostasis. Combined thrombin and plasmin generation (T/P-G) assays have been recently
described, and we have adapted the technique to investigate the interplay between
coagulation and fibrinolysis in patients with various haemostatic disorders. Our modified
T/P-G was initiated by the addition of a mixture of optimised lower concentrations
of tissue factor and tissue-type plasminogen activator. Thrombin generation (TG) and
plasmin generation (PG) were monitored simultaneously using individual fluorescent
substrates in separate microtitre wells. The relationship between coagulation and
fibrinolysis was demonstrated by analysing the effects of thrombin inhibitors, activated
protein C and thrombomodulin. The most evident impairments in TG were observed with
plasma samples deficient of coagulation factors participating in the prothrombinase
complex. Defects in PG were observed with deficiencies of factor (F)V, FX, fibrinogen,
and plasminogen. TG appeared to be a prerequisite for the initiation of PG, and overall
PG was governed by fibrinogen concentration. TG in patients with haemophilia A correlated
with levels of FVIII activity, but there was no significant relationship between PG
and FVIII:C, confirming that the abnormal haemostasis in haemophilia A results in
a severe imbalance between coagulation and fibrinolysis. The findings demonstrate
that global haemostasis depends on a sensitive balance between coagulation and fibrinolysis,
and that the modified T/P-G assay could provide an enhanced understanding of haemorrhage
and thrombosis in clinical practice.
Keywords
Thrombin generation - plasmin generation - coagulation - fibrinolysis - global haemostatic
assay