The dRVVT Screen Ratio is a key component of lupus anticoagulant (LA) testing. It is calculated from the dilute Russell's viper venom time (dRVVT) screen test, which uses a low-phospholipid reagent to increase sensitivity to lupus anticoagulant. A normal dRVVT screen ratio is typically less than 1.20, while an elevated ratio (≥1.20) may suggest the presence of LA. However, elevated results can also arise from coagulation factor deficiencies, anticoagulant medications, or other inhibitors.
The screen ratio is determined by dividing the patient’s plasma clotting time by the clotting time of normal pooled plasma. When the ratio is elevated, additional tests, such as mixing studies and confirmatory assays, are often performed to distinguish lupus anticoagulant from other causes of prolonged clotting times.
The dRVVT screen ratio is frequently used in combination with other tests, such as aPTT, as part of a comprehensive lupus anticoagulant panel. When incorporated into a reflexive testing algorithm, it has a sensitivity of approximately 65-70% for diagnosing lupus anticoagulant. This multi-step approach enhances diagnostic accuracy, particularly when interpreting complex coagulation abnormalities.
dRVVT Screen Ratio
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