dRVVT Screen (reflexes to dRVVT Confirm Ratio)
|Profile or Test Panel|
|Also Known as (Alias)||lupus anticoagulant; diluted Russell viper venom|
|Test Information||Lupus Anticoagulants (LAC) refer to auto antibodies against negatively charged phospholipids or complexes of phospholipids with either beta-2-glycoprotein 1 or clotting factors such as prothrombin. They occur in various clinical conditions, especially autoimmune diseases and are now considered to be a significant risk factor in patients with otherwise unexplained thrombosis and may be present in women who have recurrent fetal loss. LAC are detected using phospholipid responsive clotting tests, such as the aPTT, Kaolin Clotting Time (KCT) and dilute Russell Viper Venom test (DRVVT). These tests have varying sensitivity to LAC depending on the LAC characteristics and the reagents used.|
|Additional Test Information||dRVVT Screen and dRVVT Confirm test is based on the following:
Russell’s viper venom present in LA 1 Screening Reagent initiate plasma clotting by directly activating factor X. LA antibodies prolong the LA 1 Screening Reagent clotting time.
LA 2 Confirmation Reagent is similar to LA 1 Screening Reagent but contains a high phospholipid concentration. The extra phospholipid counteracts the LA antibody and significantly corrects the clot time.
DRVV test “bypasses” factor VII of the extrinsic pathway as well as contact and antihemophilic factors of the intrinsic pathway. Therefore LA 1 Screening Reagent is more specific for LA than APTTs as they are not affected by contact factor abnormalities or by factor VIII deficiencies or antibodies.
Mixing tests may be useful to exclude factor II, V and X deficiencies, which may prolong LA 1 Screening Reagent and LA 2 Confirmation Reagent results. Mixing normal plasma with test plasma replenishes any factors deficient in the test plasma. If the mixing test is still prolonged, it indicates that an inhibitor is present in the test plasma.
|Sample Requirements||Whole Blood: 3.2% Sodium Citrated (blue top) OR
|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
|Minimum Volume or Pediatric volume||Frozen Plasma: at least 0.5ml in 2 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 ambient 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 ice
|Requisition Form||RFT- Hemostasis Reference Laboratory|
|Test Schedule||Monday – Friday|
|Turn around Time (analytic time)||5 Business Days|
|Report/ Results||Fax number required to receive report|