Which test is commonly used to screen for lupus anticoagulant in antiphospholipid syndrome?

• A. dRVVT (dilute Russell viper venom test)
• B. Bleeding time
• C. Platelet aggregation with ristocetin
• D. Fibrinogen level

Answer: (A)

Lupus anticoagulant causes prolongation of clotting times in tests that rely on a phospholipid surface, reflecting its interference with phospholipid-dependent steps of the coagulation cascade. The dilute Russell viper venom test is designed to reveal this interference because venom activates the common pathway in a way that requires phospholipid surfaces; if lupus anticoagulant is present, it binds phospholipid-binding proteins and disrupts this surface, leading to a prolonged clotting time. Because of its phospholipid dependency, this test is widely used as a screening tool for lupus anticoagulant in antiphospholipid syndrome. If LA is suspected, follow-up testing with mixing studies or phospholipid-neutralizing steps helps confirm the presence of an inhibitor rather than a true factor deficiency. The other options do not screen for lupus anticoagulant: bleeding time assesses primary hemostasis, ristocetin-induced platelet aggregation evaluates platelet–vWF interaction, and fibrinogen level measures a clottable protein but does not detect antiphospholipid antibodies.