Table 1

Factors of the coagulation and fibrinolysis system found to be raised in rheumatoid arthritis (RA)

Function
Coagulation factors
 Tissue factor (TF)Initiator of blood coagulation pathways (extrinsic pathway)
 Von Willebrand factor (vWF)Binds to other proteins (FVIII), important in platelet adhesion to wound sites
 Factor VIII (FVIII)Essential blood clotting protein: cofactor to factor IXa
 Activated factor XII (FXIIa)Activates factor XI and prekallikrein (contact activation or intrinsic pathway)
 Prothrombin fragments 1+2 (F1+2)Prothrombinase complex (FXa+FVa) converts prothrombin (FII) to thrombin (FIIa) and F1+2
Fibrinolysis factors
 FibrinogenPlasma glycoprotein that is converted by thrombin into fibrin during blood clot formation
 Tissue plasminogen activator antigen (t-PA)Key enzyme in plasmin formation from plasminogen
 Plasminogen activator inhibitor-1 (PAI-1)Inhibits plasmin formation by inhibiting t-PA
 D-dimerFibrin degradation product
 Thrombin-activatable fibrinolysis inhibitor (TAFI)Fibrinolysis inhibitor: cleaves C-terminal lysines from partially digested fibrin and reduces activation of plasminogen, leading to delayed clot lysis