THE TEXTARIN ECARIN RATIO - A CONFIRMATORY TEST FOR LUPUS ANTICOAGULANTS/

Lupus anticoagulants (LA) are immunoglobulins (IgG, IgM, IgA or a mixt ure) which interfere with in vitro phospholipid (PL) dependent tests o f coagulation (e.g. APTT, KCT, dilute Russell Viper Venom Time). LA ar e heterogeneous; consequently, the laboratory diagnosis is difficult a nd relies on multiple tests. We have developed a sensitive and relativ ely specific confirmatory test system based on fractions of two snake venoms. Textarin(R), a protein fraction of Pseudonaja textilis venom ( Australian Eastern brown snake), activates prothrombin in the presence of PL, factor V and calcium ions. Ecarin, a protein fraction of Echis carinatus venom, will activate prothrombin in the absence of any cofa ctors. The activation of prothrombin by Textarin yields thrombin while Ecarin yields meizothrombin. In the presence of LA, the Textarin time is prolonged and the Ecarin time is unaffected. The test results are reported as a ratio of Textarin/Ecarin times (abnormal greater than 1. 3). We have evaluated this test system in the following patient popula tions: LA positive, therapeutically heparinized, stable oral anticoagu lated, liver disease, routine preoperative, anticardiolipin antibody p ositive LA negative, hemophilia A, various other hereditary factor def icien cies or dysfunctional proteins, and specific inhibitors of facto r V and factor VIII. The LA positive patients represented a mixed popu lation of autoimmune disease, drug-induced and post-infectious states. Our findings indicate the sensitivity of the Textarin/ Ecarin system in the confirmation of LA. In order to use the test system most effect ively, it is recommended to incorporate polybrene with Textarin when e valuating heparinized samples. Factor V deficiency and specific inhibi tors of factor V yielded, in some instances, false positive results.