VFE Plates

VFE is an enzyme-linked immunoassay (ELISA) for quantifying von Willebrand factor (vWF, also called factor VIII-related antigen) in human plasma. This plasma protein factor is deficient or defective in patients with von Willebrand's disease, a relatively common inherited disorder associated with an increased tendency to bleed. Laboratory studies in these patients usually demonstrate:

1) A decrease in procoagulant activity as measured by activated partial thromboplastin time;

2) A prolonged bleeding time; and

3) A decreased plasma concentration of vWF.

A major diagnostic problem concerns the differentiation of patients with von Willebrand disease from those with classical Hemophilia A (factor VIII coagulant deficiency). Patients with the latter disorder have a decrease in plasma procoagulant activity (i.e. a prolonged activated partial thromboplastin time) but have normal or increased concentration of vWF in the plasma. The VFE assay affords rapid differentiation of these two disorders.

VFE is also of use in identifying carriers of Hemophilia A, a sex-linked disorder; under most circumstances only males have bleeding problems. The affected males inherit the gene for Hemophilia A from their mothers who carry the involved gene, but have no bleeding problems.

In order to determine if a woman is a carrier of Hemophilia A, it is necessary to measure factor VIII coagulant activity and vWF concentration. The ratio of factor VIII coagulant activity to vWF concentration in carrier females is approximately 0.5 while the ratio in normal females is 1.0.

This Kit is Intended for In Vitro Diagnostic Use Only

	Copyright Ati Atlas Ltd 2009

Human Specimens: Calibrators provided in this kit contain plasma obtained from human donors. Each donor's serum was tested by FDA approved methods for the presence of antibodies to HIV-1 and hepatitis B surface antigen and found to be negative for both.

However, since no test method can absolutely guarantee the absence of these or other infectious agents, all Calibrators and human plasma tested with this assay should be handled in accordance with NCCLS guidelines for preventing the transmission of blood-borne infections during laboratory procedures. Wear gloves and avoid contact with skin and mucous membranes.

WARNING: The Stop Solution in this kit contains hydrochloric acid. Avoid ingestion or contact with skin or eyes.

VFE

Kit Contents

Product Code

Human von Willebrand Factor Calibrator: 2 vials containing 0.5ml of prediluted lyophilised human plasma with a known vWF concentration, borate saline buffer, bovine serum albumin, sheep serum, EDTA and ProClin 300™ as a preservative. The concentration of vWF in the Calibrators was determined by comparison to World Health Organisation International Reference material (97/586).
At least fifteen minutes prior to use, reconstitute a vial of the Calibrator by carefully adding exactly 0.50ml of deionised, distilled water to the vial, briefly vortexing to mix and solubilise the diluted plasma, and allow to stand at room temperature for 15 minutes prior to use. The reconstituted Calibrator solution is stable at 2 - 8C for a maximum of 4 weeks.
Microtiter Wells: 8 (eight) 12 × 1 microtiter well Strips (96 total wells) coated with rabbit immunoglobulin isolated from antiserum specific for human vWF and stabilised in dry form. The Wells are provided in a resealable foil pouch containing a desiccant packet.
Plate Sealing Tape: 2 Sheets
Microplate Frame: 1
Specimen Diluting Buffer: 1 vial containing 45 ml of borate-saline buffer, bovine serum albumin, normal rabbit serum, normal sheep serum, ethylenediaminetetraacetate (EDTA) and ProClin 300™ as a preservative.
HRP-Conjugated Anti-vWF: 1 vial containing 22 ml of HRP-conjugate sheep antibody in a diluent of saline, normal sheep serum, a commercial stabilising agent and ProClin 300™ as a preservative.
Substrate: 1 amber plastic bottle containing 22 ml of 3,3',5,5'-tetramethylbenzidine (TMB) one component substrate, in an acidic buffer, with 0.01% hydrogen peroxide. Because of its extreme sensitivity, avoid exposing this reagent to light, borosilicate glass and elevated temperatures. As supplied, the Substrate should be colourless, slightly amber or slightly bluish tinted. DO NOT USE THIS SUBSTRATE IF IT IS DEEPLY BLUE IN COLOR BEFORE ADDITION TO THE MICROWELLS.
At the final stage of incubation, remove from refrigerator and measure the amount of Substrate required for the current assay, using only plastic pipet materials, recap the bottle and return to 2 - 8C storage. The material removed should be stored in the dark and allowed to slowly come to ambient temperature prior to addition to the washed microwells.
Stop Solution: 1 vial containing 12 ml of 1% hydrochloric acid.

VE-98

VFE Kit Availability