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LUPUS ANTICOAGULANT(DRVVT)
The lupus anticoagulant is an acquired autoantibody found in various autoimmune disorders & sometimes in otherwise healthy individuals. These immunoglobulins bind to certain proteins when bound to phospholipids. The effective sequestration of phospholipid can then cause prolongation of phospholipid dependant coagulation tests such as PT and APTT.The presence of these antibodies in the plasma leads to prolongation of PT and APTT in vitro (anticoagulants), however in vivo they are associated with thrombotic tendencies including recurrent venous thrombo-embolism, cerebro-vascular accidents & arterial events. It is also associated with recurrent abortions, fetal loss & other complications of pregnancy.
Lipus anticoagulants (LA) are autoantibodies against anionic phospholipid portion of prothrombinase.Prothrombinase is a complex of factor Xa factor Va phospholipid & calcium ions involved in the conversion of prothrombin to thrombin in the coagulation pathway. The autoantibodies produced are of IgG class orIgM class or both as these type antibodies were first detected in- patients with SLE they were named LA. LA's prolong phospholipid dependent tests such as the activated partial thromboplastin time (APTT) & kaolin clotting time (KCT).The nameanticoagulant is a misnomer since patients do not have a bleeding tendency ,instead there is a clear association of thrombo-embolism.LA is also an important cause of recurrent abortions in women. Since these antibodies are also found in patients with SLE detection of LA is important in management of patients with or without SLE experiencing unusual thrombotic events & habitual abortions. The dilute russell's viper venom test (d RVVT) was first introduced by thiagarajan et al in 1986.dRVVT is a simple sensitive and specific assay for detection of LA since russell's viper venom activates factor x directly, dRVVT is more specific for LA than APTT .Results are affected neither by contact factor
