Molecular testing to confirm a phenotypic diagnosis of von Willebrand disease type 2A.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA) or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
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.
Clinical Sensitivity: 99 percent for vWD type 2A and 80 percent for types 2B and 2M; unknown for other vWD subtypes.
Methodology: Bidirectional sequencing of VWF exon 28 and its intron-exon boundaries; if no pathogenic mutations are detected, bidirectional sequencing of exons 11, 12, 14, 15, 16, 24, 25, 51, and 52 and the corresponding intron-exon boundaries is performed.
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 exons 11, 12, 14, 15, 16, 24, 25, 28, 51 and 52 are not evaluated.
|Component Test Code*||Component Chart Name||LOINC|
|2005481||vWD Type 2A (VWF) Sequencing Specimen|
|2005482||vWD Type 2A (VWF) Sequencing Interp|
- VWD platelet type 2A reflex
- VWF2A Sequencing