DiaPharma Group, Inc.

Intended use

Automated latex enhanced immunoassay for the quantitative determination of von Willebrand Factor Activity (VWF Activity) in human citrated plasma on IL Coagulation Systems. This product is for in vitro diagnostic use.

Summary and principle

The diagnosis of von Willebrand Disease (VWD), probably the most common congenital bleeding disorder, requires a number of special tests at the laboratory level. The measurement and comparison of von Willebrand Factor Antigen (VWF:Ag), VWF Activity and Factor VIII (FVIII) levels in plasma aid in the differentiation of quantitative defects (type 1 or type 3) or qualitative defect (type 2) of VWF and therefore to diagnose the different types of VWD.

When an extremely low or undetectable level of VWF:Ag is obtained, a type 3 VWD could be expected. If a moderate or even normal result is obtained, VWF Activity and FVIII assays must be performed and compared with the

VWF:Ag result. If all three values are within the normal range, VWD and Hemophilia A may be excluded. If at least one parameter is abnormally low, it is necessary to calculate the ratios VWFActivity/VWF:Ag and FVIII/VWF:Ag. If both ratios are close to 1 (some authors suggest 0.7 as cut-off), a VWD type 1 may be diagnosed.

When the VWF/Activity/VWF:Ag ratio is low (0.7 is also the suggested cut-off), types 2A, 2B or 2M may be diagnosed. These subtypes are characterized by its abnormal multimeric pattern and/or its altered platelet affinity.Additional laboratory tests as RIPA (Ristocetin Induced Platelet Aggregation), multimeric analysis and binding assays are required in order to be able to distinguish the different subtypes.

When the FVIII/VWF:Ag ratio is low (0.7 is also the suggested cut-off), a type 2N or Hemophilia A may be diagnosed and a FVIII binding assay is necessary to discriminate among them.

The VWF Activity kit is a latex particle enhanced immunoturbidimetric assay to quantify VWF Activity in plasma. The activity of VWF is determined by measuring the increase of turbidity produced by the agglutination of the latex reagent. A specific anti-VWF monoclonal antibody adsorbed onto the latex reagent, directed against the platelet binding site of VWF (Glycoprotein Ib receptor), reacts with the VWF of patient plasma. The degree of agglutination is directly proportional to the activity of VWF in the sample and is determined by measuring the decrease of transmitted light caused by the aggregates.

Reagent -- Composition, Packaging, Storage and Stability

• Latex Reagent (Cat. No. 0020004710): 2 vials x 4.5 mL of a lyophilized suspension of polystyrene latex particles coated with purified anti-VWF mouse monoclonal antibody directed against a functional epitope of VWF, containing bovine serum albumin, stabilizers and preservative. Stability after reconstitution: 1 month at 2-8°C in the original vial, 3 days at 15°C on the ACL® 8000/9000/10000 or 1 day on the ACL Futura®/ACL Advance Systems. Do not freeze.
• Buffer (Cat. No. 0020004720): 2 vials x 4.5 mL of Tris buffer containing bovine serum albumin, stabilizers and preservative.

Unopened reagents are stable until the expiration date shown on the vial when stored at 2-8°C. For optimal stability remove reagents from the system and store them at 2-8°C in the original vial.

Additional reagents and control plasmas
The following are not supplied with the kit and must be purchased separately.

• Calibration Plasma (Cat. No. 0020000000)
• Normal Control (Cat. No. 0020003120)
• Special Test Controls Level 1 & 2 (Cat. No. 0008467600)
• Factor diluent (Cat. No. 0009757600)