The activity level for factor IX needed to ensure clotting is around 30%.
In the event of a severe accident, it may be necessary to achieve circulating levels of 50%, or even 80% for heavy surgery.
Prophylaxis and treatment involve the administration of plasma-derived or recombinant factor IX concentrates.
In the presence of anti-factor IX antibodies, recombinant factor VIIa may be used, as well as activated prothrombin complex concentrates such as Feiba®(1).
Other therapeutic measures may be adopted in certain specific situations.
Desmopressin (Minirin®) cannot be used in haemophilia B. (1) Factor Eight Inhibitor Bypassing Activity
Monitoring involves measurement of factor IX activity levels, as well as screening for, and assay of, specific inhibitors.
In patients treated with recombinant activated factor VII, the activity of this substance should be measured.
Recent studies have shown that global coagulation tests such as the thrombin generation test may constitute useful and effective tools for the adaptation of replacement therapy in patients presenting an inhibitor.