Introduction: The primary aim in the treatment of patients with hemophilia A is the prevention
of bleeds with factor VIII (FVIII) replacement therapy. One major adverse event of
factor VIII replacement therapy is the developement of alloantibodies (FVIII inhibitors).
These antibodies may show a neutralizing effect on FVIII activity, resulting in an
inadequate recovery after intravenous FVIII application and an increase in bleeding
episodes. In hemophilia care the repetitive examination of the patients’ inhibitor
status is mandatory. The functional Bethesda assay has a broad acceptance as a standard
procedure, although it is difficult in performance, standardization and costly. Immunoassays
for detection of Factor VIII antibodies have been introduced. Data from a nationwide
cohort study in the US suggests to replace the costly clotting assay by an immunoassay
using recombinant Factor VIII as antigen.
Methods: FVIII inhibitor testing was performed with dilutional FVIII clotting assay (Technoclone,
Factor VIII Inhibitor Kit™) and anti-FVIII immunoassay (Hyphen Biomed, Zymutest™ anti-FVIII
IgG mono strip).
Results: We examined 322 blood samples obtained from 203 pediatric and adult with haemophilia
A on FVIII replacement therapy.
Conclusion: Discordant results were only detected in the Bethesda assay negative results (< 0,4
BU). We found a considerable number of borderline reactive samples (28%, 91/322) and
8% (26/322).
