However, due to a lack of international consensus on methods for the laboratory testing of factor VIII levels in plasma, we would not currently recommend the measurement of factorVIII levels as part of routine thrombophilia screening.
These new approaches include replacement therapy with porcine factor VIII concentrate (currently approved for use in acquired hemophilia patients), bispecific antibodies to simulate the biologic function of factor VIII (already in use in some jurisdictions), pegylated forms of activated factor VII, and strategies targeting the natural anticoagulants TFPI and antithrombin, which create a hypercoagulable phenotype to counterbalance the hypocoagulability imposed by hemophilia.
Hypercoagulability may be caused by an increase in the level of various coagulation factors such as factor (F) VIII, FX, FIX, von Willebrand F (vWF), and fibrinogen, while hypofibrinolysis by changes in coagulation parameters such as a decrease in plasmin and plasmin activator or an increase in α2-antiplasmin, plasminogen activator inhibitor-1 and thrombin activatable fibrinolysis inhibitor.
Of 146 patients with primary osteonecrosis, 65 (45%) had none of the 5 thrombophilias (Factor V Leiden heterozygosity, high levels of Factors VIII and XI, anticardiolipin antibody immunoglobulin M, and homocysteine) that otherwise distinguished patients with osteonecrosis from control subjects (P<.05).
A thrombophilia screen post-partum revealed a significantly elevated factor VIII level and a hypercoagulable state that justified prolonged anticoagulation.
The major thrombophilias in the arthroscopy group were factor V Leiden heterozygosity (40%), high factor VIII level (50%), and high homocysteine (30%).
A subsequent magnetic resonance venography of his head revealed venous thrombosis, and other investigations revealed an elevated factor VIII level as well as a mutation at the MTHFR locus, consistent with an elevated risk for hypercoagulability.
Thrombophilia was suspected and the relative investigation revealed high levels of factor VIII procoagulant, which is frequent in hemodialysis patients, and resistance to activated protein C. Polymerase chain reaction detected that the patient was heterozygous for factor V Leiden, which is quite common in general population.
Although our patient is a smoker, used oral contraceptives and was found to have a heterozygote mutation at the factor V Leiden gene, the most important factor contributing to her thrombophilia is thought to be her significantly elevated factor VIII.
We carried out serologic measures of thrombophilia (homocysteine, anticardiolipin antibodies [ACLA] immunoglobulin G and immunoglobulin M, lupus anticoagulant, factor VIII, factor XI, protein C, total and free protein S, antithrombin III) and hypofibrinolysis (plasminogen activator inhibitor activity [PAI-Fx], lipoprotein[a]).
The case with factor VIII of 160% had two other thrombophilias (compound MTHFR C677T-A1298C heterozygosity, resistance to activated protein C), and hypofibrinolytic high Lp(a).
Newly described abnormalities associated with thrombophilia include the syndrome of activated Protein C resistance (APCR), the prothrombin 20210A mutation, hyperhomocysteinemia, and elevated levels of coagulation factors VIII and XI.
We conclude that high factor VIII:Ag levels are a highly prevalent risk factor for venous thrombosis and contribute to risk in families with thrombophilia, and that these high levels are likely to be genetically determined by factors other than just blood group.