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A two‐step coagulation test to identify antiβ 2 ‐glycoprotein I lupus anticoagulants
Author(s) -
Pengo V.,
Biasiolo A.,
Pegoraro C.,
Iliceto S.
Publication year - 2004
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/j.1538-7836.2004.00712.x
Subject(s) - antibody , lupus anticoagulant , coagulation , medicine , coagulation testing , prothrombin time , chemistry , immunology , microbiology and biotechnology , biology
Summary. Lupus anticoagulants (LA) are immunoglobulins which inhibit phospholipid (PL)‐dependent coagulation tests. LA are not specific, as they may reflect the presence of antibodies to human prothrombin, human β 2 ‐Glycoprotein I (β 2 GPI), an association of previous antibodies or other antibodies. Antibodies to human β 2 GPI act as in vitro anticoagulants by enhancing the binding of β 2 GPI to PL, and this binding may be influenced by calcium ion concentration. A reduction in final calcium concentration, from 10 m m to 5 m m , increased coagulation times in both dilute Russell Viper Venom Time (dRVVT) and dilute Prothrombin Time (dPT) when plasmas of patients with antiβ 2 GPI antibodies were used. Ten LA patients showed increased dRVVT and dPT ratios from means of 1.5 to 1.7 ( P < 0.001) and 2.4 to 4.3 ( P = 0.002), respectively. Instead, all LA‐positive antiβ 2 GPI antibody‐negative patients showed decreased coagulation times from mean ratios of 1.5 to 1.3 ( P = 0.004) in dRVVT and from 2.0 to 1.5 ( P = 0.01) in dPT. These results are confirmed by running dRVVT of normal plasma spiked with affinity purified IgG antiβ 2 GPI antibodies. Therefore, when a PL–dependent coagulation test is run twice, at different final calcium concentrations, antiβ 2 GPI LA can be identified.