A Sensitive Test Demonstrating Lupus Anticoagulant and its Behavioural Patterns

Abstract

The kaolin clotting time of platelet poor plasma was used as a sensitive test for detecting the lupus anticoagulant in mixtures of normal and patients' plasmas. Platelets were found to decrease the anticoagulant effect of a typical lupus inhibitor. Thus, high sensitivity in this test system was achieved by ensuring low platelet concentrations and omitting platelet lipid substitute. In 17 patients with disseminated lupus erythematosus (DLE), 12 had detectable inhibitor by this method, more than would be detected with routine coagulation tests. Mixing patterns were of four distinct types, representing three different modes of anticoagulant behaviour. The pattern (type 3) of plasma mixtures giving longer kaolin clotting times than the individual components could be reproduced in vitro by adding trace amounts of crude thrombin or platelet fragments to a more typical lupus anticoagulant-containing plasma; formation of such a mixing pattern by the plasma of a patient with DLE may therefore indicate activation of the coagulation pathway. Six patients with idopathic thrombocytopenic purpura (ITP) had no detectable inhibitor indicating that anti-platelet antibodies behave differently from the lupus anticoagulant.

Intracellular events in platelet activation induced by antiphospholipid antibodies in the presence of low doses of thrombin

“…Anti-␤ 2 GPI activities were determined at 405 nm, with results expressed in net OD units. LAC activities of the IgG and of the F(abЈ) 2 fragments were determined by a modified activated partial thromboplastin time (APTT) as previously described (20).…”

Antiphospholipid antibodies affect trophoblast gonadotropin secretion and invasiveness by binding directly and through adhered β2-glycoprotein I

“…The presence of LAC was evaluated using different assays, i.e., standard activated partial thromboplastin time, kaolin clotting time (39), tissue thromboplastin inhibition test (40), and dilute Russell's viper venom time. These tests were performed according to the guidelines of the Scientific and Standardization Committee of the International Society on Thrombosis and Hemostasis (41).…”

Antiphospholipid antibodies induced in mice by immunization with a cytomegalovirus‐derived peptide cause thrombosis and activation of endothelial cells in vivo

“…The LAC activity of the TIFI-induced aPL mAb was determined using modified kaolin clotting time (KCT) testing, as previously described (23). Briefly, 50 l of the test mAb (ϳ15 g/ml) was mixed with 50 l of normal human plasma.…”