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vWF Exon 28 Gene Analysis

Item Value
Approval req'd? Yes, contact Hematology lab at 353-1747
Available Stat? No
Utilization Guidelines REASONS FOR TESTING:
á Confirm diagnosis of variant von Willebrand Disease (VWD).
á Diagnose difficult cases of Type 2A, 2B and 2M VWD.
á Facilitate genetic counseling and prenatal diagnosis.

Results are reported as:
Normal – Normal DNA Sequence
Abnormal – Presence of mutation known to cause Type 2A, 2B, or 2M VWD.

Sequencing of Exon 28 of VWF can be used to diagnose type 2B von Willebrand disease. If a mutation is not found in VWF Exon 28 for a patient whose platelets aggregate to low dose ristocetin, the alternative diagnosis of platelet-type von Willebrand disease should be considered. Sequencing of the GP1BA gene could be used to confirm a diagnosis of platelet-type von Willebrand disease.

Sequencing of Exon 28 of VWF can be used to diagnose most cases of type 2M von Willebrand disease. Twenty-four of thirty-one distinct 2M mutations noted in the von Willebrand Disease mutation database (http://vwf.group.shef.ac.uk/; 2M-specific variants accessed on March 12, 2013) are located in VWF exon 28. If a patient exhibits a ristocetin cofactor activity/von Willebrand factor antigen ratio <0.4 on more than one occasion and has a normal VWF Exon 28 sequence, complete VWF gene sequencing could be performed. [Of note, 2 rare 2M mutations of VWF (W1745C and S1783A) have been described that exhibit normal ristocetin cofactor activity, normal von Willebrand factor antigen, and a normal multimer pattern but are deficient in collagen binding.

A von Willebrand Factor Collagen Binding assay (performed at Quest Diagnostics) may be requested by contacting the Parnassus Hematology laboratory at 353-1747.)
Test code MOLT (Order in Apex as 'Miscellaneous Outside Lab Test' using the complete test name above)
Performed by ARUP
Sendout? Yes
Method PCR-Direct DNA Sequencing
Collection Instructions A completed patient history form MUST be submitted with the sample.

Click here for form
Container type Lavender top or Yellow top (ACD)
Amount to Collect 3 mL blood
Sample type EDTA or ACD whole blood
Preferred volume 3 mL blood
Min. Volume 1 mL blood
UCSF Rejection Criteria Wrong sample type.
Processing notes Deliver immediately to Hematology for processing.
Ref Lab Rejection Criteria Sample > 72 hours old at room temperature when received.

Sample > 7 days old refrigerated when received.
Normal range
Normal Normal DNA Sequence
Abnormal Presence of mutation known to cause Type 2A, 2B, or 2M VWD.
Synonyms vWD gene 28 mutation
Turn around times 3 weeks
CPT coding 83891-90, 83892-90 X2, 83898-90 X 2, 83904-90 X 4, 83912-90, 81403-90
Last Updated 2/16/2016 12:46:39 PM
Entry Number 1325
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