Antiphospholipid antibodies and recurrent pregnancy loss: correlation between the activated partial thromboplastin time and antibodies against phosphatidylserine and cardiolipin.

Concordance was determined among the presence of the lupus anticoagulant measured by prolongation of the activated partial thromboplastin time and IgG and IgM antibodies against phosphatidylserine and cardiolipin in 47 patients selected for study because of histories of recurrent spontaneous pregnancy loss and a positive test for at least one antiphospholipid antibody. Forty-five of 47 patients (96%) had a prolonged activated partial thromboplastin time, ranging from 46 to 150 seconds. Elevated levels of IgG antiphosphatidylserine antibodies and IgM antiphosphatidylserine antibodies were present in 41 (87%) and in 19 (40%) of samples, respectively. Antibodies against cardiolipin were less commonly observed; IgG anticardiolipin antibodies in only 32 (68%) of 47 samples and IgM anticardiolipin antibodies in 15 (36%) of 42 samples. Neither the level of IgG antiphosphatidylserine antibodies nor the level of IgG anticardiolipin antibodies correlated well with the degree of prolongation of coagulation in the activated partial thromboplastin time (R = 0.312, p = 0.032 for IgG antiphosphatidylserine antibodies versus activated partial thromboplastin time; R = 0.251, p = 0.088 for IgG anticardiolipin antibodies versus activated partial thromboplastin time). Concordance with the activated partial thromboplastin time, however, was observed in 41 (87%) samples for IgG antiphosphatidylserine antibodies and in only 32 (68%) samples for IgG anticardiolipin antibodies. Our conclusion is that the antiphosphatidylserine assay correlates best, although not totally, with the presence of lupus anticoagulant and that the antiphosphatidylserine assay is more sensitive than testing for anticardiolipin.