Aim: The antiphospholipid syndrome (APS) is defined by the laboratory detection of at least one of three antiphospholipid (aPL) autoantibodies (lupus anticoagulant (LA), anti-cardiolipin (aCL) or anti-β2-glycoprotein I antibodies (aβ2GpI)) and the clinical manifestation of either thrombosis or pregnancy morbidity in a patient. Recognising APS and administering appropriate therapy is important to reduce risk of recurrent venous and/or arterial thrombosis, and to prevent pregnancy morbidity. In some instances, patients having clinical manifestations highly suggestive of APS are persistently negative for these antibodies but instead have other aPL autoantibodies. Antiprothrombin (aPT), antiphosphatidylserine/prothrombin (aPS/PT), anti-annexin A5 (aANXA5) and anti-β2-glycoprotein I Domain I (aβ2GpI DI) antibodies have been associated with increased risk of thrombosis in various studies. This has led to proposals for some of these antibodies to be considered another of the APS criteria antibodies. We aim to determine the prevalence of aPT, aPS/PT, aANXA5 and aβ2GpI DI among patients with unprovoked venous thrombosis.
Method: Sera from 155 patients who had undergone laboratory testing for the current APS criteria antibodies were enrolled in the study. IgG and IgM aPT (Demeditec Diagnostics), aPS/PT (Inova Diagnostics) and aANXA5 (Demeditec Diagnostics) antibody assays were performed manually by traditional ELISA method. IgG aβ2GpI DI (IL/Werfen) antibody assays were performed by chemiluminescent immunoassay method using the HemosIL® AcuStar.
Results: IgG aPT, aPS/PT, aANXA5 and aβ2GpI DI was detected in 13.6%, 10.3%, 6.5% and 5.2% of patients respectively. IgM aPT, aPS/PT and aANXA5 was detected in 4.5%, 7.7% and 1.3% of patients respectively. LA, IgG aCL and aβ2GpI was detected in 2.6%, 3.9% and 1.2% of patients, respectively. In this cohort, the prevalence of APS non-criteria antibodies was higher than APS criteria antibodies.
Conclusion: The detection of these APS non-criteria autoantibodies has potential therapeutic implications for patients with unprovoked venous thrombosis as long-term anticoagulation will be indicated.