Which test is commonly used to screen for lupus anticoagulant due to its sensitivity to phospholipid-dependent reactions?

Which test is commonly used to screen for lupus anticoagulant due to its sensitivity to phospholipid-dependent reactions?

• A. dRVVT
• B. PT
• C. aPTT
• D. Reptilase Time

Answer: (A)

Lupus anticoagulant antibodies specifically disrupt phospholipid-dependent steps in coagulation, so tests that rely on a phospholipid surface are prolonged when LA is present. The dilute Russell viper venom test is designed to reveal this sensitivity: it uses venom to trigger the common pathway, but with a limited amount of phospholipid available to form the prothrombinase complex. If lupus anticoagulant is present, it binds phospholipids and markedly delays clotting, and doing the test in a diluted fashion increases this sensitivity, making it a reliable screen for LA. In contrast, the prothrombin time uses tissue factor to start coagulation and isn’t geared to detect LA. The aPTT can be affected by LA but is not specific enough as a screen because many factors can prolong it. The reptilase time uses a phospholipid-independent enzyme and is not affected by lupus anticoagulant, so it isn’t useful for screening LA.

Lupus anticoagulant antibodies specifically disrupt phospholipid-dependent steps in coagulation, so tests that rely on a phospholipid surface are prolonged when LA is present. The dilute Russell viper venom test is designed to reveal this sensitivity: it uses venom to trigger the common pathway, but with a limited amount of phospholipid available to form the prothrombinase complex. If lupus anticoagulant is present, it binds phospholipids and markedly delays clotting, and doing the test in a diluted fashion increases this sensitivity, making it a reliable screen for LA.

In contrast, the prothrombin time uses tissue factor to start coagulation and isn’t geared to detect LA. The aPTT can be affected by LA but is not specific enough as a screen because many factors can prolong it. The reptilase time uses a phospholipid-independent enzyme and is not affected by lupus anticoagulant, so it isn’t useful for screening LA.