Von Willebrand Factor (VWF) is a large multimeric plasma protein with important functions in primary hemostasis. VWF is synthesized in endothelial cells and megakaryocytes as pre-pro-VWF. After various posttranslational modifications and cleavage of the signal peptide, the propeptide (VWF:PP) is also cleaved off by the protease furin in the trans-Golgi-system.
A non-covalent complex of VWF and VWF:PP remains stored in Weibel-Palade bodies (endothelium) or in a-granules (megakaryocytes). Activation or stimulation of these cells will release the complex. VWF and VWF:PP dissoclate and metabolize with different half lives. While VWF has a half-life of approx. 12 hours, VWF:PP is metabolized with a half-life of only approx. 2 hours.
The molar ratio of VWF:PP to VWF can be used as an indicator for the degradation of VW F. An increased ratio of VWF:PP to VWF indicates increased clearance of VWF. These are found in various patients with congenital VWF deficiency, but also in acquired VWF syndrome.
An accurate knowledge of the clearance of VWF may influence the choice of therapy, in particular the need to administer VWF concentrates. lncreased levels of VWF:PP or an abnormal ratio between VWF:PP and VWF may also be caused by activation of the endothelium or platelets.
The calibration is performed against the International Standard.
Control and calibrator are included in the kit.
- 12 strips with 8 wells coated with an anti-VWF:PP monoclonal antibody
- 1 x 6 mL of anti-VWF:PP monoclonal antibody coupled to an enzyme,
- 1 x 12 mL of substrate solution,
- 1 x 15 mL of stop solution,
- 2 x 25 mL of sample diluent,
- 1 x 100 mL of concentrated wash buffer,
- 1 vial of freeze-dried calibration plasma
- 1 vial of freeze-dried control plasma
- 1 plastic frame
- 1 sheet with calibrator and control values
