Molecular testing to confirm a phenotypic diagnosis of von Willebrand disease type 2M.
- 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 type 2M.
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 exons 28, 30, and 31.
Clinical Sensitivity: 80 percent for vWD types 2A, 2B, and 2M; unknown for other vWD subtypes.
Methodology: Bidirectional sequencing of VWF exons 28, 30, 31 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 exons 28, 30, and 31 will not be evaluated.
|Component Test Code*||Component Chart Name||LOINC|
|2005491||vWD Type 2M (VWF) Sequencing Specimen|
|2005492||vWD Type 2M (VWF) Sequencing Interp|
- VWD type 2M sequencing assay
- VWF2M Sequencing