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Lupus Anticoagulant (LA)

No single screening test can detect all LA-positive patients. Several tests are available and at least two should be employed to verify the presence of LA. Before any LA screening test is done, a thrombin time (TT) should be performed to rule out therapeutic heparin or the presence of a thrombin (factor-II) inhibitor.

These are some of the LA screening procedures that can then be used:

  • Dilute Russell's Viper Venom time (DRVVT). This test utilizes a reagent containing venom from the viper Vipera russelli (which activate factor V and X), low levels of phospholipids, and calcium ions in a clotting time test. The DRVVT test principle is based on the idea that the reagents can help to identify the antibody's dependence on phospholipids .
  • Platelet neutralization procedure. This assay will show the dependence on phospholipids for the lupus anticoagulant to take effect. This can be performed using the aPTT based technique, with the DRVVT test, or using Taipan snake venom time tests.
  • Kaolin clotting time or silica clotting time
  • Hexagonal Phospholipid test (HPP). This is a similar assay to the platelet neutralization procedure, but thought to be more sensitive.