Molecular testing to distinguish von Willebrand disease type 2N from hemophilia A.
- 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. Symptoms of type 2N are similar to mild hemophilia A.
Incidence: Approximately 1 in 100 to 1 in 1000 individuals.
Inheritance: Autosomal recessive.
Cause: Pathogenic VWF mutations.
Clinical Sensitivity: Unknown for VWD type 2N.
Methodology: Bidirectional sequencing of VWF exons 4, 9, 17, 18, 19, 20, 21, 24, 25, and 27 and the corresponding 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 4, 9, 17, 18, 19, 20, 21, 24, 25, and 27 will not be evaluated.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|2005495||VWD Type 2N (VWF) Sequencing Specimen|
|2005496||VWD Type 2N (VWF) Sequencing Interp|
- VWD type 2N sequencing assay
- VWF2N Sequencing