Rox Factor VIII

Rox Factor VIII is a chromogenic kit for the determination of Factor VIII (FVIII) activity in human plasma and FVIII containing concentrates. This kit is for in vitro research use only and should not be used for patient diagnosis or treatment.

FVIII is a plasma protein of about 230 000 Daltons (230kD), which serves as a cofactor to Factor IXa in its activation of Factor X to Factor Xa. Deficiency of FVIII causes the severe bleeding disorder Hemophilia A. FVIII is stabilized by its binding to von Willebrand Factor (vWF), a multimeric glycoprotein which prolongs the half-life of FVIII in blood circulation.

Key characteristics

• Excellent dilutional linearity over the whole measuring range, also at very low Factor VIII levels.
• Excellent discrimination at low Factor VIII activities.
• Conditions during activation are in agreement with the European Pharmacopoeia chapter 2.7.4 Assay of human coagulation factor VIII.
• One range, only one calibration curve is used for the whole measuring range 0 – 2 IU/mL (0-200%).
• Factor VIII deficient plasma not needed.
• Stability of Reagents after reconstitution 72 hours at 2-8℃.
• Reagents can be aliquoted and frozen at ≤ -70℃ in order to limit reagent waste.
• Not sensitive to Emicizumab due to use of bovine Factor X instead of human Factor X.
• Compared to FVIII kits with only bovine components, the Rox Factor VIII kit contains human FIXa which ensures proper interaction with plasma derived as well as recombinant human Factor VIII.
• Use calibrator and control plasmas calibrated vs. an international standard.

Measurement principle

In the presence of Ca2+ and phospholipids, Factor X is activated to Factor Xa by Factor IXa. This reaction is greatly stimulated by FVIII after activation to FVIIIa by thrombin. By using optimal concentrations of Ca2+, phospholipids and an excess of Factor IXa, Factor X and thrombin, the rate of activation of Factor X is directly related to the amount of FVIII in the sample. Factor Xa hydrolyses the chromogenic Factor Xa substrate, Z-D-Arg-Gly-Arg-pNA, thus liberating the chromophoric group pNA. The colour is read photometrically at 405 nm and the generated FXa and thus the intensity of colour is proportional to the FVIII activity in the sample.

Kit information

• 1 Kit = 2 x 100 tests (manual microplate method).
• Limit of detection 0.003 IU/mL (0.3%) FVIII.
• Measuring range 0 – 2 IU/mL (0 – 200%) FVIII.
• For In Vitro Research Use Only.
• Calibrator or Control plasmas not included – use plasmas calibrated vs. an international standard.