Coexistence of anti-beta(2)-glycoprotein I domain I and anti-phosphatidylserine/prothrombin antibodies suggests strong thrombotic risk

Abstract

Background: Highly specific assays for measuring antiphospholipid antibodies (aPLs) are required for accurate assessment of thrombotic risk. aPLs against beta(2)-glycoprotein I domain I (anti-beta 2GPIdI) and against prothrombin complexed with phosphatidylserine (anti-PS/PT) have been recently identified as being associated with a hypercoagulable state. This study evaluated the synergism between anti-beta 2GPIdI and anti-PS/PT for predicting thrombotic events. Methods: A total of 180 patients with clinical suspicion of hypercoagulability were evaluated. The plasma levels of lupus anticoagulant (LA) and antibodies against anticardiolipin (anti-CL) (IgG and IgM), beta 2GPI (IgG and IgM), PS/PT (IgG and IgM), and beta 2GPI dI (IgG) were measured. Results: IgG anti-beta 2GPIdI and LA were highly associated with thrombosis. Mean values and positivity rates of IgG anti-beta 2GPI dI and IgG anti-PS/PT were significantly higher in the triple-positive group (LA+, IgG anti-CL+, IgG anti-beta 2GPI+) than in the other groups. Interestingly, the thrombotic risk [odds ratio 9OR) 24.400, 95% confidence interval (CI) 1.976-63.273, p < 0.001] of the newly defined triple positive group (LA +, IgG anti-CL +, IgG anti-beta 2GPIdI +; OR 11.182, 95% CI 1.976-63.273, p = 0.006) was more than twice that of the triple-positive group (LA +, IgG anti-CL +, IgG anti-beta 2GPI +). Double positivity for IgG anti-PS/PT and IgG anti-beta 2GPI also indicated significant thrombotic risk (OR 7.467, 95% CI 2.350-23.729, p = 0.001). Furthermore, the thrombotic risk associated with double positivity for IgG anti-PS/PT and IgG anti-beta 2GPIdI was markedly elevated (OR 33.654, 95% CI 6.322-179.141, p < 0.001). Conclusions: Our data suggest that simultaneous measurement of IgG anti-beta 2GPIdI and IgG anti-PS/PT may improve clinical decision-making for aPL-positive patients.