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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: · Confirm diagnosis of variant von Willebrand Disease (VWD). · Diagnose difficult cases of Type 2A, 2B and 2M VWD. · Facilitate genetic counseling and prenatal diagnosis. Results are reported as: Normal – Normal DNA Sequence OR 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 (testing available at Blood Center of Wisconsin). 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 at Blood Center of Wisconsin if clinically indicated. [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 hematology laboratory at 353-1747.) |
| Test code | MOLT |
| Performed by | Blood Centers of Wisconsin |
| Sendout? | Yes |
| Method | PCR-Direct DNA Sequencing |
| Container type | Lavender top |
| Amount to Collect | 5 mL blood |
| Sample type | EDTA whole blood |
| Preferred volume | 5 mL blood |
| Min. Volume | 3 mL blood |
| UCSF Rejection Criteria | Wrong sample type. |
| Processing notes | Deliver immediately to Hematology for processing. |
| Ref Lab Rejection Criteria | Sample > 72 hours old when received |
| Normal range | NEG |
| Synonyms | vWD gene 28 mutation |
| Turn around times | 3 weeks |
| Additional information | REASONS FOR TESTING: · Confirm diagnosis of variant von Willebrand Disease (VWD). · Diagnose difficult cases of Type 2A, 2B and 2M VWD. · Facilitate genetic counseling and prenatal diagnosis. Results are reported as: Normal – Normal DNA Sequence OR 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 (testing available at Blood Center of Wisconsin). 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 at Blood Center of Wisconsin if clinically indicated. [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 hematology laboratory at 353-1747.) |
| CPT coding | 83891-90, 83892-90 X2, 83898-90 X 2, 83904-90 X 4, 83912-90, 81403-90 |
| Last Updated | 3/24/2013 7:02:32 PM |
| Entry Number | 1325 |
If you have additional questions regarding this test, please call: 415-353-1667