VWF Activity by Ristocetin Cofactor
| Profile or Test Panel |
Bleeding Diathesis with a Normal APTT/PT Profile
VWD Profile
If the APTT is prolonged and the factor VIII is normal, this panel reflexes to an APTT Reflexive Evaluation Profile.
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| Indications | Requires VW Antigen and FVIII levels to interpret results |
| Method | Turbidometric |
| Test Information | Ristocetin is a negatively charged antibiotic that induces platelet agglutination in vitro. Plasma vWF activity is determined by the ability of patient’s plasma to support ristocetin-induced agglutination of normal formalin-fixed platelets. Reduced levels are characteristic of von Willebrand disease. Elevated values may occur with stress, inflammation, pregnancy, estrogen therapy, or exercise. |
| Additional Test Information | Normal Range: 37-154% effective 11/1/11 |
| Sample Requirements | Whole Blood: 3.2% Sodium Citrated (blue top) OR Frozen Plasma |
| Requested Volume | Two 5 ml 3.2 sodium citrated (blue top) tubes as whole blood OR Frozen plasma in 4 X 1mL aliquots in plastic tubes |
| Sample Information | Whole blood is preferred for testing but if it is not possible to send whole blood tubes TO ARRIVE HERE WITHIN 3 HOURS of collection then send frozen plasma. To prepare plasma centrifuge blue top tubes at 1500g for 15 minutes and remove the plasma and centrifuge a second time at 1500g for an additional 15 minutes. Aliquot approximately 1 ml of plasma into 4 plastic tubes, and freeze. |
| Shipping Information | Whole Blood: Send at amibient temperature (18-25C) and must be received within the lab in less than or equal to 3 hours after collection. Frozen Plasma: send on dry iceSend samples to: Bloodworks Northwest For additional information, please see Ordering Information |
| Requisition Form | RFT- Hemostasis Reference Laboratory |
| Transaction Code | 3210-03 |
| CPT Codes | 85245 |
| Turn around Time (analytic time) | Run once weekly; depending upon requests, available STAT. |
| Report/ Results | Fax number required to receive report |