THU0343 Recurrent Thrombosis in Young Patients with Primary Antiphospholipid Syndrome: The Relevance of The Antiphospholipid Antibody Profile
Authors: M. Rodrigues, C. Nalli, L. Andreoli, E. Balestreri, A. Zanola, F. Allegri, A. Pedrini, G.L. Norman, M. Mahler, A. Tincani
Journal: Annals of the Rheumatic Diseases (2016)

<h3>Background</h3> 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. <h3>Objectives</h3> To determine the risk factors for rethrombosis in patients with PAPS. <h3>Methods</h3> 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 &lt;0.1 in univariate analysis were included. Anti-DI was not included because data were not available for the whole cohort. P-values &lt;0.05 were considered statistically significant. <h3>Results</h3> 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&lt;0.001), OA (19% vs 46% p=0.009) and anti-platelet treatment (37% vs 59% p&lt;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). <h3>Conclusions</h3> 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. <h3>Acknowledgement</h3> This project was made possible by an EULAR scientific training bursary <h3>Disclosure of Interest</h3> 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