Global Haemostatic Methods Following Administration of Bypassing Agents to Patients With Haemophilia With Inhibitors

Background The treatment of haemophilia A and B has been revolutionized by the use of factor concentrate, both as prophylaxis and to treat bleeding episodes (on-demand treatment). However, despite its advantages, repeated treatment with factor concentrate can lead to development of inhibitors (antibodies) towards the coagulation factor in the concentrate. Another patient group in which the bleeding symptoms are difficult to treat because of inhibitors towards coagulation factors, most commonly FVIII, is patients with acquired haemophilia. Patients with high antibody titers exhibit a deficient or no response to factor concentrates and usually need treatment with bypassing agents, namely factor eight inhibitor bypassing agent (FEIBA®, Baxter) och recombinant activated factor VII (rFVIIa, Novo-Seven®, Novo Nordisk). The effect of the treatment cannot be accurately monitored by traditional coagulation tests. The aim of the study is to evaluate the utility of the global haemostatic methods in patients with haemophilia with inhibitors. The objective is to improve the monitoring of the treatment effect and thus increase the safety of the patient and the effectiveness of the treatment. Patients and methods Patients The primary cohort will consist of fifteen patients with inherited haemophilia with inhibitors as well as five adult patients with acquired haemophilia who are followed up at the Coagulation Department of the Karolinska University Hospital, Stockholm, Sweden. Blood samples will be collected from those patients at specific time points (see Design of the study) during the course of two years (for each patient). The treatment (type, dose, duration) will be determined by the treating physician. Methods (selection) * Thrombin generation (Calibrated Automated Thrombogram, CAT® and a commercial kit from Siemens®). * Overall haemostatic potential (OHP) Design of the study Timeframe for blood sampling: i) baseline (inclusion in the study), and ii) prior and after administration of bypassing agents to either treat bleeding symptoms or before an invasive procedure or as prophylaxis. Data analysis The variations in coagulation markers measured as described above (Methods) will be associated to the clinical symptoms (bleeding), the level of coagulation factors (if measurable) and the titers of the inhibitors.