Ordering Recommendation

Molecular testing to confirm a phenotypic diagnosis of von Willebrand disease type 2B and to distinguish from pseudo (platelet-type) VWD.

Mnemonic
VWF2B SEQ
Methodology

Polymerase Chain Reaction/Sequencing

Performed

Varies

Reported

14-21 days

New York DOH Approval Status
Specimens from New York clients will be sent out to a New York DOH approved laboratory, if possible.
Specimen Required
Patient Preparation
Collect

Lavender (EDTA), pink (K2EDTA) or yellow (ACD Solution A or B).

Specimen Preparation

Transport 3 mL whole blood. (Min: 1 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions
Remarks
Stability

Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable

Reference Interval

By report

Interpretive Data

Background Information for von Willebrand Disease, Type 2B (VWF) Sequencing:
Characteristics
: Mucocutaneous bleeding after brushing or flossing teeth, unexplained bruising, prolonged repeated nosebleeds, menorrhagia, and prolonged bleeding following childbirth, trauma or surgery.
Incidence
: Approximately 1 in 100 to 1 in 1000 individuals.
Inheritance:
Autosomal dominant for types 2B, 2M and most of 2A; autosomal recessive for 20 percent of 2A.
Penetrance:
Dominant mutations are incompletely penetrant when VWF:Ag and VWF:RCo levels are 25-50 IU/dL.  Full penetrance is expected when VWF:Ag and VWF:RCo levels are less than 25 IU/dL.
Cause
: Pathogenic VWF mutations in exon 28.
Clinical Sensitivity
: 80 percent for vWD types 2A, 2B, and 2M; unknown for other vWD subtypes.
Methodology:
Bidirectional sequencing of VWF exon 28 and its intron-exon boundaries.
Analytical Sensitivity and Specificity
: 99 percent.
Limitations
: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations, deep intronic mutations, and large deletion/duplications will not be detected. Mutations lying outside of VWF exon 28 are not evaluated.

Compliance Category

Laboratory Developed Test (LDT)

Note
Hotline History
N/A
CPT Codes

81403

Components
Component Test Code* Component Chart Name LOINC
2005487 vWD2B (VWF) Specimen
2005488 vWD Type 2B (VWF) Sequencing Interp
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • VWD type 2B sequencing assay
  • VWF2B Sequencing
von Willebrand Disease, Type 2B (VWF) Sequencing