COMPARISION OF THE DETECTION OF LUPUS ANTICOAGULANTS USING THREE DIFFERENT METHODS AND THE PRESENCE OF ANTI-CARDIOLIPIN ANTIBODIES

Lupus anticoagulant (LAC) is an antibody directed against phospholipids which prolongs in vitro clotting assays. Several detection methods have been described; however all give some different results. Recently ELISA and RIA assays have been developed which detect IgG and IgM anti-cardiolipin antibodies. The aim of our study was to compare three different LAC tests with an ELISA anti-cardiolipin test. The tests used were : kaolin clotting time (KCT or Exnertest), tissue thromboplastin inhibition test (TTI or Schleider test), activated partial thromboplastin time using a 50, 100, 200 fold dilution of the phospholipid preparation (APTT dilution test), and an IgG and IgM anti-cardiolipin ELISA test. 114 samples of patients suffering from diseases known to be accompanied with LAC antibodies (auto-immune diseases, recurrent abortion, thromboembolism, etc.) were studied. Positivity with one of the tests was found in 45 patients (39%). Patients with the diagnosis of SLE or otherimmune diseases showed the highest positivity (56%) whereas those with thromboembolism, recurrent abortion etc. were only positive in 27%.

Among these 45 positive patients the TTI was positive in 41 cases (91 %);however in 10 cases (24 %) this was the only positivity found. The KCT test and the APTT dilution test were both positive in 18 cases (40 %). Anti-cardiolipin antibodies were found in 21 patients (47 %): IgG only in 12 (27 %), IgM only in 5 (11 %), both IgG and IgM in 2 (4 %); in 19 of these 21 patientsthe TTI was also positive.

In our study the TTI test seems to be the most sensitive test but possibly also the test with the highest aspecific positivities. IgG and IgM anti-cardiolipin antibodies were less frequently found than expected.