Comparison of the factor VII : C clot analysis and a modified activated factor VII analysis for monitoring factor VII activity in patients treated with recombinant activated factor VII (NovoSeven (R))
M. Johannessen et al., Comparison of the factor VII : C clot analysis and a modified activated factor VII analysis for monitoring factor VII activity in patients treated with recombinant activated factor VII (NovoSeven (R)), BL COAG FIB, 11, 2000, pp. S159-S164
Bleeding episodes in haemophilia A and B inhibitor patients are now frequen
tly treated with recombinant activated factor VII (NovoSeven(R), Novo Nordi
sk A/S, Bagsvaerd, Denmark). Until now, the FVII:C coagulation assay has be
en used to monitor NovoSeven(R)-mediated coagulation. However, a new assay
(Staclot VIIa-rTF, Diagnostica Stage, France) has been designed to specific
ally detect activated factor (F)VII. Replacement of the buffer supplied by
the manufacturer with a PIPES buffer containing BSA (modified FVIIa assay),
resulted in a linear standard curve, greater sample stability and a reduce
d coefficient of variation. The FVII:C assay and the modified FVIIa assay w
ere compared in a recovery experiment using the International FVIIa standar
d No 89/688(IS). Recovery of FVIIa was 93-97% for the modified FVIIa assay
and 91-115% for the FVII:C assay. However, because samples in the FVII:C as
say were not parallel to the standard curve, confidence limits for recovery
were as wide as 67-130% compared with 92-106% for the FVIIa assay. In conc
lusion, a modified version of the Staclot VIIa-rTF assay, suitable for moni
toring treatment with NovoSeven(R), even at low concentrations, has been de
veloped. It provides an alternative to the FVII:C assay, which is not suita
ble for monitoring FVIIa at low concentrations. Blood Coagul Fibrinolysis 1
1 (suppl 1):S159-S164 (C) 2000 Lippincott Williams & Wilkins.