Safety and efficacy of factor XI (FXI) concentrate use in patients with FXI deficiency: a single-centre experience of 19 years.

Aim: Factor XI (FXI) concentrate is a pooled human plasma-derived factor concentrate used as replacement therapy for patients with FXI deficiency, which provides a predictable response and consistent haemostatic cover in emergency or elective situations. It has previously been implicated in adverse events such as thrombosis and inhibitor formation, with rare case reports of fatal incidents. We sought to establish the incidence of such complications in a retrospective case series between 1994 and 2012 at the Haemophilia Comprehensive Care Centre at Royal Free Hospital, London, UK.

Methods: Patients who received FXI concentrate had their medical records reviewed to extract information and specific adverse events recorded such as failure of treatment with further bleeding, suspected viral transfusion transmitted infection (TTI), thrombosis or inhibitor formation.

Results: Eighty-six patients received 242 treatment episodes of FXI concentrate. Ninety percent of treatment episodes were covered with BPL FXI concentrate and 10% with LFB Hemoleven. Twelve (5%) adverse events were recorded, with eight (3.3%) of all treatment episodes were related to persistent bleeding postconcentrate infusion and there were 4 (1.7%) non-bleeding adverse events. No viral TTIs were identified. There were two recorded inhibitors, one thrombotic event (central retinal artery occlusion) and one transfusion reaction. No patient suffering an adverse event resulted in long-term morbidity.

Conclusion: Our experience of FXI concentrate use demonstrates infrequent minor adverse events related to its administration and is a safe product to use.