Association of autoantibodies against the phosphatidylserine–prothrombin complex with manifestations of the antiphospholipid syndrome and with the presence of lupus anticoagulant

TLDR

The study aimed to determine how antiprothrombin antibodies relate to antiphospholipid syndrome clinical features and lupus anticoagulant presence. The authors evaluated 265 autoimmune disease clinic patients, measuring IgG/IgM antiprothrombin antibodies (aPS/PT and aPT) by ELISA, assessing anticardiolipin and β2GPI dependency, and testing lupus anticoagulant with three assays. aPS/PT antibodies were strongly associated with APS clinical manifestations and with lupus anticoagulant, showing similar specificity to β2GPI‑dependent anticardiolipin, whereas aPT antibodies were not; thus, aPS/PT positivity may serve as a thrombotic risk marker in autoimmune patients.

Abstract

Objective To clarify the association of autoantibodies against prothrombin with the clinical manifestations of the antiphospholipid syndrome (APS) and with the presence of lupus anticoagulant (LAC). Methods We examined 265 patients who visited our autoimmune disease clinic. IgG and IgM antiprothrombin antibodies were tested by enzyme-linked immunosorbent assay (ELISA) as either antiphosphatidylserine–prothrombin complex (aPS/PT) antibodies or as antibodies against prothrombin coated on irradiated ELISA plates (as antigen) (aPT). IgG, IgM, and IgA anticardiolipin (aCL) antibodies and their β2-glycoprotein I (β2GPI) dependency were also evaluated by ELISA. LAC was tested by 3 different methods. Results The presence of aPS/PT, but not of aPT, significantly correlated with the clinical manifestations of APS (odds ratio [OR] 4.39, 95% confidence interval [95% CI] 2.06–9.38), and aPS/PT antibodies were as specific as β2GPI-dependent aCL for APS (93.1% for both). IgG aPS/PT strongly correlated with the presence of LAC as detected using the dilute Russell viper venom time test (OR 38.2, 95% CI 13.4–109.1). Conclusion Antiprothrombin antibodies are heterogeneous and their clinical relevance depends on the method of detection applied. Positive results on the aPS/PT test can serve as a marker of thrombotic events in patients with autoimmune diseases.