THU0343 Recurrent Thrombosis in Young Patients with Primary Antiphospholipid Syndrome: the Relevance of the Antiphospholipid Antibody Profile

Background Recurrence of thrombosis in patients with Primary Antiphospholipid Syndrome (PAPS)is a major event yielding to poor prognosis.The identification of risk factors for recurrence is crucial to improve secondary prophylaxis strategies. Objectives To determine the risk factors for rethrombosis in patients with PAPS. Methods Retrospective analysis of a monocentric cohort of patients with thrombotic PAPS defined according to the updated Sapporo Criteria. aPL were determined by Lupus Anticoagulant (LA), anti-cardiolipin (aCL) IgG/IgM and anti-β2 glycoproteinI (anti-β2GPI) IgG/IgM. A positive result by all 3 assays was defined as triple positivity.Retrospective collection of serum samples was possible for 107 patients (66%).Ninety-two patients with positive anti-β2GPI IgG (57%) were selected for testing IgG against the domain I of β2GPI (anti-DI)using the chemiluminescence immunoassay in BIO-FLASH®system (INOVA Diagnostics, San Diego, CA, USA; cut-off 20CU). High titre anti-DI was defined as above 60CU.Patients were grouped by the number of events (single – S or recurrent – R). Comparisons between groups were performed using chi square and Mann-Whitney. Multivariate logistic regression was used to identify independent determinants of R events.Variables identified as having p-value <0.1 in univariate analysis were included. Anti-DI was not included because data were not available for the whole cohort. P-values <0.05 were considered statistically significant. Results The study included 162 PAPS patients (118 female, median age 48 years; venous thrombosis, VT – 103, arterial thrombosis, AT – 59). During the follow-up 70 recurrences were observed in 53 patients (VT – 36, AT – 34). Patients with rethrombosis more frequently had cardiac disease (hypertensive cardiopathy, valvular dysfunction, patent foramen ovale) (43% vs 21% p=0.007) and arterial hypertension (53% vs 33% p=0.01). Recurrent events were significantly associated with triple positivity (64% vs 44% p=0.01), LA (83% vs 62% p=0.008) and anti-β2GPI IgM (77% vs 60% p=0.03). Patients with rethrombosis less frequently received hydroxychloroquine (HCQ) (11% vs 41% p<0.001), OA (19% vs 46% p=0.009) and anti-platelet treatment (37% vs 59% p<0.001). The logistic regression analysis showed that triple positivity (OR 3.57 95%CI 1.32–9.65), cardiac dysfunction (OR 3.51 95%CI 1.35–9.15), HCQ (OR 0.22 95%CI 0.08–0.64), OA (OR 0.06 95%CI 0.02–0.24) and anti-platelet treatment (OR 0.01 95%CI 0.03–0.34) remained significant. Triple aPL positivity was more frequent in younger patients (under 50 years, n=118) who had recurrent events (71% vs 51% p=0.05), while no differences were found in terms of traditional cardiovascular risk factors. In the subgroup of anti-β2GPI IgG positive patients, recurrence was associated with the presence of high titre anti-DI in the whole cohort (80% vs 50% p=0.006) and in patients below the age of 50 (80% vs 55% p=0.03). Anti-DI levels were significantly higher in patients with recurrence (median 316CU vs 61CU p=0.02). Conclusions Patients with thrombotic PAPS still develop recurrence despite treatment.Triple positivity and high titre anti-DI conferred an increased risk of rethrombosis irrespective of traditional risk factors. Acknowledgement This project was made possible by an EULAR scientific training bursary Disclosure of Interest M. Rodrigues: None declared, C. Nalli: None declared, L. Andreoli: None declared, E. Balestreri: None declared, A. Zanola: None declared, F. Allegri: None declared, A. Pedrini: None declared, G. L.Norman Employee of: Inova Diagnostics, M. Mahler Employee of: Inova Diagnostics, A. Tincani: None declared