Pseudo-von Willebrand disease: GP1Ba Sequencing

Diagnostic Use

Pseudo-von Willebrand disease (Pseudo-VWD) is a rare autosomal dominant bleeding disorder that results from a gain-of-function mutation. Pseudo-VWD, also known as platelet type VWD, results from an abnormally high affinity interaction between the platelet glycoprotein Ib (GPIb) and its adhesive ligand von Willebrand factor (VWF), leading to characteristic platelet hyperaggregability. Rapid clearance of high molecular-weight VWF multimers from plasma, together with thrombocytopenia caused by an increased removal of the aggregated platelets, contribute tot eh bleeding problems experienced by patients with pseudo-VWD including frequent sever nosebleeds and excessive bleeding following surgical operations. The conditions share most of the clinical and laboratory features of type IIB VWD and the final discrimination between these conditions requests either platelet-mixing studies or a molecular genetic analysis.

Department

Genetics - Molecular Pathology

Delphic Registration Code

MOLP

Constituent Tests

• Genomic DNA Extraction

Synonyms

platelet type VWD

Turnaround Time

4 weeks

Specimen Type

• Whole Blood

Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

4.0

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

1.0

Minimum Sample Volume (ml)

0.5

Additional Specimen Information

This test requires nucleated cells. Please do not centrifuge or freeze blood samples.
If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Aliquot Instructions

Sample Type

• Whole Blood

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Additional Referral/Aliquot Information

Please do not centrifuge or freeze blood samples.
If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Test Method

Coding regions of exons and flanking intronic sequences of the GPIBA gene are amplified by PCR and analysed by automated fluorescent bi-directional DNA sequencing.

Contact Canterbury Health Laboratories on +64 3 364 0484 or email LabInfo@cdhb.health.nz

Uncertainty of Measurement:
Automated bidirectional DNA sequencing has an analytical sensitivity and specificity of >99%. Note that the lower limit of variant detection of sequencing analysis is ~10%, this is important to consider in the case of mosaicism, mitochondrial, and somatic variation that is not expected to be present at 50% or 100%. This analysis will not detect variants located within intronic regions, except at the intron-exon boundaries.

Genomic DNA must be extracted from the specimen prior to testing. This incurs an additional charge (see GDNA). Laboratories may prefer to submit DNA for testing. Please provide a minimum of 5 micrograms of DNA at 20 nanograms/microlitre.

Contact Information

Enquiry Form