Description

The Lupus Anticoagulant (LA) is an autoantibody associated with antiphospholipid syndrome (APS), an autoimmune disorder characterized by abnormal blood clotting. Despite its name, the Lupus Anticoagulant is not specific to lupus; it can occur in people with various autoimmune disorders or even in individuals without any underlying autoimmune condition.

The Dilute Russell’s Viper Venom Time (DRVVT) assay is one of the laboratory tests used to detect the presence of Lupus Anticoagulant. Here’s how it works:

1. Principle: The DRVVT assay is based on the ability of the Russell’s Viper Venom to activate the coagulation pathway. In the presence of lupus anticoagulant, there is a prolonged clotting time compared to normal plasma due to interference with the coagulation process.
2. Procedure: In the DRVVT assay, patient plasma is mixed with an excess of an activator (phospholipid) and a source of calcium. Then, Russell’s Viper Venom (a snake venom) is added. The time it takes for the plasma to clot is measured and compared to the clotting time of a normal plasma sample.
3. Interpretation: If the patient’s plasma takes significantly longer to clot compared to the normal control, it suggests the presence of lupus anticoagulant. The result is typically reported as a ratio, known as the DRVVT ratio, which compares the patient’s clotting time to that of the control plasma.
4. Limitations: While the DRVVT assay is sensitive to lupus anticoagulant, it can also be influenced by other factors such as heparin, factor deficiencies, and certain medications. Therefore, it’s essential to interpret the results in conjunction with the patient’s clinical history and other laboratory tests.

Overall, the DRVVT assay is a valuable tool in diagnosing and monitoring patients with suspected APS and evaluating their risk of abnormal blood clotting. It’s often used in combination with other tests, such as the activated partial thromboplastin time (aPTT) and the anti-cardiolipin antibody test, to confirm the diagnosis of APS.