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HelpTest Code VWD8B von Willebrand Disease 2N (Subtype Normandy), Plasma
Additional Testing Requirements
VWAG / von Willebrand Factor Antigen, Plasma; VWACT / von Willebrand Factor Activity, Plasma; and F8A / Coagulation Factor VIII Activity Assay, Plasma are recommended to supplement results of this test.
Necessary Information
If performed at another laboratory, forward the results of the following tests with the specimen:
-von Willebrand factor antigen
-VWF activity (ristocetin cofactor, latex immunoassay etc)
-Factor VIII activity
These results aid in the interpretation of this test.
Specimen Required
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing
2. Centrifuge, transfer all plasma into a vial, and centrifuge plasma again.
3. Aliquot plasma into a separate tube leaving 0.25 mL in the bottom of the centrifuged vial.
4. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, less than or equal to -40° C.
Additional Information:
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. Each coagulation assay requested should have its own vial.
Forms
If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.
Useful For
Diagnosing von Willebrand disease (VWD) type 2N
Evaluating patients diagnosed with mild-to-moderate hemophilia A with an autosomal inheritance pattern
Evaluating hemophilia A patients with a shortened survival of infused factor VIII (FVIII) (not caused by a specific FVIII inhibitor)
Evaluating female patients with low FVIII activity and no prior family history of hemophilia A
Evaluating patients with Type 1 or Types 2A, 2B, or 2M VWD with FVIII activity discordantly lower than the von Willebrand factor antigen level
Special Instructions
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name
VWD 2N (Normandy), PSpecimen Type
Plasma Na CitSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Cit | Frozen | 56 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Clinical Information
von Willebrand disease (VWD) is a bleeding disorder due to quantitative or qualitative defects in von Willebrand factor (VWF), which results from disease-causing alterations in the VWF gene. VWD constitutes 1 of the 2 most common bleeding disorders. Most subtypes of VWD are inherited as autosomal dominant traits, although autosomal recessive variants occur.
In hemostasis, there are 2 essential roles for VWF. The first is its ability to promote platelet adhesion to damaged vessel walls, and the second is to function as a carrier protein for Factor VIII (FVIII). Thus, noncovalent binding of FVIII to VWF is necessary for normal survival of FVIII in the blood circulation. In patients with severe VWD, the circulating half-life of endogenous or infused FVIII is shorter than expected. Disease-causing alterations within the FVIII binding domain of VWF may result in an isolated 'deficiency' of FVIII associated with a clinically mild to moderate bleeding disorder that may be misdiagnosed as Hemophilia A (HA).
Abnormal binding of FVIII to VWF can be detected with a binding assay. Since its initial description in patients from the Normandy region of France, more recent studies suggest that VWD type 2N or Normandy (VWD2N) has been associated with a more severe phenotype among patients who are homozygous for pathogenic alterations within the FVIII binding domain of VWF.
In an international survey, FVIII binding defect was detected in 58 out of 1198 (4.8%) patients with mild HA. Other studies confirm these findings and reveal that 1.5% to 16.6% of patients with VWD Type 1 have the FVIII binding defect. The diagnosis of VWD2N has 2 main implications:
-Genetic counseling differs considerably from that for X-linked recessive HA since the inheritance of VWD2N is autosomal recessive.
-Optimal treatment or prophylaxis of bleeding requires factor replacement therapy with products containing functional VWF.
Reference Values
68-106%
Pediatric reference ranges have not been established for this assay but likely achieve adult reference range by 18 years of age.
Interpretation
A reduced capacity of a patient's von Willebrand factor (VWF) to bind to recombinant factor VIII (FVIII) is consistent with von Willebrand disease (VWD) type 2N (Normandy).
A mild to moderate decrease of the VWF to factor VIII (FVIII) binding ratio suggests the presence of a VWD Type 2N due to heterozygous variants in the FVIII binding domain of VWF. If clinically indicated, DNA sequence analysis of the FVIII binding domain of VWF may provide useful information.
Results do not exclude other variants of congenital VWD, eg, type 1, 2A, 2B, or 2M or congenital hemophilia A. Clinical correlation should be made between patient and family bleeding history and results of VWF antigen, factor VIII and VWF activity assays.
Day(s) Performed
Monthly on the third Thursday
Report Available
1 to 31 daysSpecimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
85246
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| VWD8B | VWD 2N (Normandy), P | 90919-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 607336 | VWF:FVIIIB | 90919-2 |
| 607337 | VWF:FVIIIB Interpretation | 48595-3 |