| Description: |
Russell’s viper initiates plasma clotting activating factor X in the presence of calcium. The activated factor X then activates prothrombin (factor II) in the presence of factor V and phospholipid. If lupus anticoagulant (LA) antibodies are present in the patient and interfere with phospholipid required for coagulation, then the dRWT will be prolonged. If this test is prolonged, a confirmatory test is performed using a high concentration of a phospholipids. The excess phospholipid will neutralize the LA antibody present in the patient’s plasma and shorten the clotting time. The final result is a ratio of the two clotting times, which is compared with the values of a reference population. A lupus anticoagulant is defined by inhibition of a phospholipid-dependent clotting assay, such as the aPTT or dRWT, which corrects with excess phospholipid. The dRWT is more specific for LA than the aPTT since it is not influenced by deficiencies of the contact intrinsic pathway factors or antibodies to factors VIII or IX. |
