Anticardiolipin antibodies (aCL), anti-beta(2)-glycoprotein I (beta(2)GPI) antibodies and lupus anticoagulant (LA) are the only laboratory tests considered within the revised criteria for the classification of the antiphospholipid syndrome (APS). Recently, the significance to assay the antibodies against phosphatidylserine-prothrombin complex (aPS/PT) has been discussed, and these antibodies, rather than antibodies against prothrombin alone, are closely associated with APS and LA. The sensitivity and specificity of aPS/PT for the diagnosis of APS were assessed in a population of patients with a variety of autoimmune disorders. The aCL and aPS/PT have similar diagnostic value for APS, and most of APS patients with aPS/PT had positive LA. Therefore, aPS/PT should be further explored, not only for research purposes, but also as a candidate for one of the enzyme-linked immunosorbent assay (ELISA)-based confirmatory test for APS associated LA.