Background and Aims

Antiphospholipid syndrome (APS) is defined by occurrence of thrombotic and/or obstetric events with the persistent presence of antiphospholipid autoantibodies i.e lupus anticoagulant (LA), anticardiolipin (aCL) and anti-b2-Glycoprotein I (ab2GPI) antibodies. Among the new antibodies regularly described in patients with APS, anti-phosphatidylserin/prothrombin (aPS/PT) antibodies seem promising, at least because of their high correlation with lupus anticoagulant positivity.

The objective of this study was to characterize the population of aPS/PT and/or anti-PT antibodies positive patients, in term of organ damage and severity of APS.

Methods

This was a prospective, monocentric, descriptive database study. Out of the 148 patients selected, 128 had thrombosis of which 64 APS were diagnosed, and 20 patients were antiphospholipid antibodies positive without thrombosis. Anti-PS/PT and anti-PT IgG and IgM were searched by ELISA.

Results

Anti-PS/PT antibodies correlated with LA (Chi2=32.5). Among the APS-suspected patients without conventional antiphospholipid antibodies 9% of patients were positive for aPS/PT .

Anti-PS/PT positive patients had similar thrombotic phenotype (p = 0.43) but had significantly more frequent renal impairment (renal failure p = 0.01 and proteinuria p = 0.04), migraine (p = 0.03) and thrombocytopenia (p = 0.001) than negative patients. In addition, tetra-positivity (aCL+,ab2GPI+, LA+,aPS/PT+) was associated with more severe APS phenotype evidenced by more thrombosis under anticoagulant treatment, and a trend of more frequent catastrophic syndrome.

Conclusions

These results, showing association of presence of aPS/PT antibodies with severe phenotype and with LAC positivity, justify their determination at the first line exploration of APS and during follow up.