In the field of hemostasis and the diagnosis of coagulation disorders, the Dilute Russell’s Viper Venom Time (DRVVT)test is a crucial tool for detecting Lupus Anticoagulants (LA). These antibodies play a central role in Antiphospholipid Syndrome (APS) and other thrombotic conditions. A thorough understanding of this test is essential for laboratory professionals to ensure accurate interpretation and reliable reporting to physicians.
What Is the DRVVT Test?
Commonly referred to as the Lupus Anticoagulant Test, the DRVVT is a specialized assay designed to detect lupus anticoagulants. Despite their name, these antibodies increase the risk of thrombosis rather than bleeding. Commercial DRVVT kits typically involve two main steps:
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dRVV Screen: Contains a low concentration of phospholipids. If LA is present, clotting time is prolonged.
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dRVV Confirm: Contains a high concentration of phospholipids to neutralize LA, resulting in a shorter clotting time.
When LA is present, the clotting time in the Confirm test is shorter than that in the Screen test.
In both reagents, Russell’s viper venom acts as a direct activator of Factor X, bypassing the upstream components of the coagulation cascade.
Key Points for Accurate DRVVT Testing
To ensure accurate results, the following points must be carefully observed:
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Sample Collection: Use citrated plasma (3.2% sodium citrate). The sample should be platelet-poor (less than 10,000 platelets/μL) and free from heparin contamination.
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Reagents: Use commercial DRVVT kits with standardized venom and phospholipid concentrations.
For more information, you can refer to the product inserts and licenses for Heamostica DRVVT kits: 
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Controls: Run both positive and negative controls with patient samples. Establish the reference range using normal pooled plasma.
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Sample Storage: Perform the test immediately or store plasma at -70°C.
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Automation: Automated coagulometers reduce human error and improve reproducibility.
Test Procedure
This test can be performed manually, semi-automatically, or with fully automated coagulation analyzers. Patient plasma is tested undiluted.
Establishing Reference Ranges
Each laboratory must define its own normal range. To do this, test at least 40 normal plasma samples for both the Screen and Confirm steps.
The reference pool derived from normal plasmas should be included in every run to calculate ratios accurately.
Reporting Results
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DRVVT Screen Result is reported as a Screen Ratio, calculated as follows:
Screen Ratio = Patient Screen Time / Reference Pool Screen TimeA ratio greater than 1.2 is considered abnormal and suggests the presence of LA. A Confirm test is then required.
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DRVVT Confirm Result is also reported as a Confirm Ratio:
Confirm Ratio = Patient Confirm Time / Reference Pool Confirm Time -
The Normalized Ratio is calculated as:
Normalized Ratio = Screen Ratio / Confirm RatioA Normalized Ratio ≥ 1.2 confirms the presence of Lupus Anticoagulant. However, for a confirmed APS diagnosis, the test must be repeated at least 12 weeks later, and the result interpreted in the context of the patient’s clinical presentation.
If the DRVVT is positive, a mixing study with normal plasma (1:1) should be performed:
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If clotting time remains prolonged, an inhibitor (like LA) is likely.
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If clotting time corrects, consider a factor deficiency.
Normal Ranges & Interpretation
Due to variations in kits and instruments, no universal normal range exists. Generally:
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DRVVT Screen: 32–42 seconds
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DRVVT Confirm: Usually shorter than Screen
However, Screen Ratio is the preferred metric:
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< 1.2: Normal
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≥ 1.2: Requires further investigation
Challenges and Limitations
The DRVVT test presents several challenges:
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Interferences: Anticoagulants like DOACs, warfarin, or heparin may prolong clotting time and mimic LA. Always review the patient’s medication history and consider alternative testing methods if needed.
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Pre-analytical Variables: Hemolysis, lipemia, or improper sample handling can impact results. Strict adherence to protocols is essential.
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Low Specificity: While DRVVT is sensitive to LA, it is not specific. Other inhibitors or deficiencies may yield false positives. Always correlate with patient history and other lab findings.
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Reference Range Variability: Due to different reagents and analyzers, each lab must establish and validate its own reference ranges.
Clinical Significance
The DRVVT test plays a critical role in diagnosing Antiphospholipid Syndrome (APS), associated with recurrent thrombosis, miscarriages, and thrombocytopenia. A positive DRVVT result, confirmed twice over a 12-week interval and supported by clinical evidence, supports an APS diagnosis. It is also useful in the evaluation of unexplained thrombosis or prolonged clotting times.
Frequently Asked Questions (FAQs) for Patients
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What is the DRVVT test and why was it ordered for me?
It’s a blood test to detect lupus anticoagulant, an antibody that may increase your risk of blood clots or pregnancy loss. Your doctor may have ordered it to investigate a history of thrombosis or miscarriages. -
Does the test hurt?
No more than a standard blood draw—it involves a quick needle stick. -
Does a positive DRVVT result mean I have a dangerous condition?
Not necessarily. A positive result suggests the possibility of an antibody, but a diagnosis depends on repeat testing and your clinical symptoms. -
Does having lupus anticoagulant mean I will bleed?
Despite the name, this antibody is linked to clotting, not bleeding. -
Is this condition treatable?
Yes. If the antibody is confirmed and poses a risk, your doctor may prescribe anticoagulants like warfarin or aspirin based on your overall condition. -
Do I need to repeat the test?
Yes, to confirm APS, the test must be repeated after 12 weeks. -
Does this affect pregnancy?
If you have a history of miscarriage or blood clots during pregnancy, this test can help guide your doctor. Treatment may be needed during pregnancy. -
Should I fast before the test?
No fasting is required, but your doctor may give instructions about your medications. -
Can my medications affect the result?
Yes. Blood thinners like heparin or warfarin can interfere. Inform your doctor or lab staff about all medications you’re taking. -
What should I do if my test is positive?
Your doctor may order additional tests or recommend treatment. Don’t worry—many people with this condition lead healthy, normal lives.
Conclusion
For laboratory professionals, the DRVVT test requires both technical knowledge and practical skill. A clear understanding of its methodology, interpretation, and limitations enables you to provide accurate and clinically valuable information to physicians.
At Heamostica.com, we are committed to empowering labs with up-to-date knowledge and tools in hemostasis diagnostics. Stay connected with us for more insights.