Incidence of a First Thrombo-Embolic Event in Patients With Systemic Lupus Erythematosus and Anti-phosphatidylserine/prothrombin Antibodies: A Prospective Study

Objective: This study aimed to prospectively investigate the incidence of first thromboembolic events (TEs) in a cohort of systemic lupus erythematosus (SLE) patients. The patients were positive for anti-phosphatidylserine/prothrombin (aPS/PT) antibodies and tested negative for anticardiolipin (aCL) and anti-β2–glycoprotein I (aβ2GPI) antibodies [regardless of their Lupus Anticoagulant (LA) status]. Methods: Inclusion criteria included: (a) SLE with no previous TEs; (b) no concomitant anti-thrombotic therapy; (c) isolated confirmed positive test for aPS/PT. Results: From the total of 52 SLE patients (42, 80.8% women), 18 patients (34.6%) were found to be positive for aPS/PT (IgG/IgM). During a mean follow-up (3.9 ± 1.1 years), 3 TEs occurred (1.3%/year). The overall cumulative incidence of TEs was 5.8% after 2 years, and up to 16.7% when focusing on aPS/PT positive patients. All the TEs events (two cerebrovascular events and one thrombotic kidney microangiopathy) occurred in the aPS/PT positive group. When focusing on IgG aPS/PT, we found that patients who tested positive were at a significantly higher risk for TEs (crude HR 19.6, 95%; CI 1.1 to 357.6; p < 0.05) compared to patients with negative aPS/PT. Conclusion: This study observed a rate of TEs of 1.3%/year, in aPS/PT positive only patients. Our prospective data suggest that aPS/PT might confer an increased risk for the development of TEs in SLE patients.