F VIII Inhibitors in Haemophilia A Patients after Continuous Infusion of Factor VIII Concentrates.

Continuous infusion (CI) of coagulation factor concentrates has been used since the early 1990s. Recent reports of the occurrence of an inhibitor (inh) after CI have raised concerns about this method of treatment. We conduct a retrospective study to investigate the development of inh after CI of FVIII concentrates in Germany. 99 haemophilia treating physicians in Germany were contacted and asked to answer a questionnaire. So far data of 13 departments have been reported and analyzed.

Three of these 13 centers never conducted a CI, in 5 no inh were detected and in 5 haemophilia centers 10 patients with inh development after CI were registered.

5 of these patients were suffering from severe, 1 from moderate and 4 from mild haemophilia (age between 7 months and 57 years). Indications for treatment were major bleeds and surgical procedures. Plasma derived (6) and recombinant (4) factor concentrates were given in various infusion sets. Data concerning infused amount (4300 to >100000 IE), exposure days (1 to >100) and inh characteristic (alloantibodies, 3 LR, 7 HR) were collected.

Regarding the genotype, we found 4 missense-mutations, 2 intron-22-inversions, 1 small deletion, 3 were unknown. In our own center we found no inh in 81 patients with major orthopaedic surgery and bolus infusion of factor VIII concentrate compared to 2 inh in 8 patients with major orthopaedic surgery and CI of FVIII.

In conclusion we found only in 2 patients the typical gene mutation for inh development. Strikingly the inh developed very often in patients with mild haemophilia. These findings agree with published results.

There might be an uncommon inh-pathomechanism due to CI or patients with mild haemophilia might exhibit a much higher prevalence of inhibitor development when treated with an “intensive FVIII-treatment” such as CI.