Dilute Russell Viper Venom Time
| Dilute Russell Viper Venom Time | | | |
| Number | | 117887 |
| CPT | | 85613 |
| Related Information | | Hemostasis and Thrombosis Appendix Lupus Anticoagulant With Reflex Stypven Time |
| Special Instructions | | If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. |
| Specimen | | Plasma (platelet poor), frozen |
| Volume | | 2 mL |
| Minimum Volume | | 1 mL |
| Container | | Blue-top (sodium citrate) tube |
Collection | | Citrated plasma samples should be collected by double
centrifugation. Blood should be collected in a blue-top
tube containing 3.2% buffered sodium citrate.1
Evacuated collection tubes must be filled to completion to
ensure a proper blood to anticoagulant ratio.2,3
The sample should be mixed immediately by gentle inversion
at least six times to ensure adequate mixing of the
anticoagulant with the blood. A discard tube is not
required prior to collection of coagulation
samples.4,5 When noncitrate tubes are collected
for other tests, collect sterile and nonadditive (red top)
tubes prior to citrate (blue top) tubes. Any tube
containing an alternate anticoagulant should be collected
after the blue-top tube. Gel-barrier tubes and serum tubes
with clot initiators should also be collected after the
citrate tubes. Centrifuge for 10 minutes and carefully
remove 2/3 of the plasma using a plastic transfer pipette,
being careful not to disturb the cells. Deliver to a
plastic transport tube, cap, and recentrifuge for 10
minutes. Use a second plastic pipette to remove the plasma,
staying clear of the platelets at the bottom of the tube.
Transfer the plasma into a LabCorp PP transpak frozen
purple tube with screw cap (LabCorp No 49482).
Freeze immediately and maintain frozen until tested. To
avoid delays in turnaround time when requesting multiple
tests on frozen samples, please submit separate frozen
specimens for each test requested.
Please print and use the Specimen
Collection Bulletin as a tube-filling guide. |
| Storage Instructions | | Freeze |
| Patient Preparation | | Avoid warfarin (Coumadin®) therapy for 2 weeks and heparin therapy for 2 days prior to the test. Do not draw from an arm with a heparin lock or heparinized catheter. |
| Causes for Rejection | | Gross hemolysis; clotted specimen; frozen specimen thawed in transit; tubes <90% full; improper labeling; specimen collected in tube other than 3.2% citrate |
| Use | | This test system is designed for the qualitative detection of lupus anticoagulants (LA) in plasma.6 |
| Limitations | | The dRVVT may be prolonged in patients with deficiencies or inhibitors of factors X, V, II, and fibrinogen. Patients on warfarin will have extended dRVVT results.7 Plasma heparin levels >1 IU/mL may interfere with this test.8 Platelets are a rich source of phospholipid that can neutralize LA. Improper preparation of the platelet-poor plasma at collection reduces the sensitivity of this assay for LA. Due to the heterogeneity of LA antibodies, no single assay will identify all cases.6 |
| Methodology | | Low phospholipid reagent consisting of Russell viper venom with excess calcium is mixed with patient plasma. The time to clot formation is measured photo-optically. |
| Additional Information | | Russell viper venom directly activates factor X in the patient's plasma. Relatively common deficiencies or inhibitors of factors VII, VIII, IX, XI, and XII do not affect the dRVVT assay. Activated factor X (Xa) forms a complex with activated factor V (Va) in the presence of phospholipid. This prothrombinase complex converts factor II (prothrombin) to IIa (thrombin). Thrombin, in turn, cleaves fibrinogen to fibrin leading to detectable clot formation. The dRVVT reagent contains a heparin inhibitor, which makes the test system insensitive to heparin levels up to 1 IU/mL.8 Lupus anticoagulants (LA) are nonspecific inhibitors of phospholipid-dependent, in vitro coagulation tests. The dRVVT reagent is diluted to ensure that it has a low phospholipid concentration, increasing the sensitivity for LA.6 The International Society on Thrombosis and Haemostasis (ISTH) has established criteria for the diagnosis of lupus anticoagulants. The ISTH has defined the minimum diagnostic criteria for LA to include:9,10 - A prolonged clot time in a screening assay such as aPTT-LA and/or dRVVT
- Mixing studies indicating the presence of an inhibitor
- Positive confirmatory studies defining phospholipid dependence of the inhibitor
- No evidence of other coagulopathies through the use of specific factor assays if the confirmatory step is negative or there is evidence of a specific factor inhibitor.
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| Footnotes | | - Adcock DM, Kressin DC, and Marlar RA, “Effect of 3.2% vs 3.8% Sodium Citrate Concentration on Routine Coagulation Testing,” Clin Pathol, 1997, 107(1):105-10.
- Reneke J, Etzell J, Leslie S, et al, “Prolonged Prothrombin Time and Activated Partial Thromboplastin Time Due to Underfilled Specimen Tubes With 109 mmol/L (3.2%) Citrate Anticoagulant,” Am J Clin Pathol, 1998, 109(6):754-7.
- “National Committee for Clinical Laboratory Standardization: Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline,” Third Edition, Villanova: NCCLS Document H21-A3:11(23), 1999.
- Gottfried EL and Adachi MM, “Prothrombin Time and Activated Partial Thromboplastin Time Can Be Performed on the First Tube,” Am J Clin Pathol, 1997, 107(6):681-3.
- McGlasson DL, More L, Best HA, et al, “Drawing Specimens for Coagulation Testing: Is a Second Tube Necessary?” Clin Lab Sci, 1999, 12(3):137-9.
- Brandt JT, Triplett DA, Alving B, et al, “Criteria for the Diagnosis of Lupus Anticoagulants: An Update. On Behalf of the Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardization Committee of the ISTH,” Thromb Haemost, 1995, 74(4):1185-90.
- Greaves M, “Antiphospholipid Syndrome: State of the Art With Emphasis on Laboratory Evaluation,” Haemostasis, 2000, 30(Suppl 2):16-25.
- DVVtest manufacturer's package insert, American Diagnostica.
- Alving BM, “The Antiphospholipid Syndrome: Clinical Presentation, Diagnosis and Patient Management,” Consultative Hemostasis and Thrombosis, Kitchens CS, Alving BM, and Kessler CM, eds, Philadelphia, PA: WB Saunders Co, 2002, 181-96.
- Levine JS, Branch DW, and Rauch J, “The Antiphospholipid Syndrome,” N Engl J Med, 2002, 346(10):752-63
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