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If you have additional questions regarding this test, please call: 415-353-1667
vWF Exon 28 Gene Analysis
|Approval req'd?||Yes, contact Hematology lab at 353-1747|
|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)|
|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.
|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|