Activation of coagulation factor XI, without detectable contact activation in dengue haemorrhagic fever.

A prospective cohort study was performed in 50 patients with dengue haemorrhagic fever (DHF) to determine the potential role of the contact activation system and factor XI activation (intrinsic pathway) in the coagulation disorders in DHF. To establish whether TAFI (thrombin-activatable fibrinolysis inhibitor) was involved in the severity of the coagulation disorders, the TAFI antigen and activity levels were also determined. Markers of contact activation (kallikrein--C1-inhibitor complexes), the intrinsic pathway of coagulation (factor XIa--C1-inhibitor complexes) and TAFI were measured and correlated to thrombin generation markers (thrombin--anti-thrombin complexes (TAT), prothrombin fragment 1+2 (F1+2)) and a marker for fibrinolysis [plasmin--alpha 2--anti-plasmin complexes (PAP)].