FRI0563 Detection of IGG Anti-Domain I Beta2 Glycoprotein I Antibodies by Chemiluminescence Immunoassay in Primary Antiphospholipid Syndrome

Background IgG anti-Domain I (anti-DI) β2 Glycoprotein I (β2GPI) antibodies are the main subset of anti-β2GPI antibodies and are associated to thrombotic risk in antiphospholipid syndrome(APS), but their detection is technically difficult because the Domain I (DI) epitope is exposed only upon a conformational change in β2GPI molecule. Chemiluminescence immunoassay (CLIA), a new fully-automated technology which exploits a light-emitting chemical reaction for antibody detection, has become available for testing anticardiolipin (aCL) and anti-β2GPI antibodies and, recently, also anti-DI antibodies. Objectives The aim of this study was to assess the clinical value of IgG anti-DI antibodies in a large homogeneous cohort of primary APS patients and in a group of ELISA-negative patients with clinical manifestations of APS. Methods The study population included 88 patients with PAPS, 63 ELISA-negative subjects and 96 controls. IgG anti-DI, IgG anticardiolipin (aCL), IgG anti-β2GPI antibodies were assayed using CLIA (HemosIL AcuStar®). Lupus Anticoagulant(LA) was assessed according to the updates international guidelines [1]. Results The sensitivity and specificity of IgG anti-DI antibodies were comparable to those of IgG aCL and IgG anti-β2GPI antibodies, while IgG anti-DI antibody sensitivity was significantly higher than that of LA (Table 1). There was a significant agreement and association (p Conclusions This study provides further evidence that anti-DI antibodies can be considered a promising biomarker for both APS classification and risk assessment particularly in patients suffering from vascular thrombosis. References Pengo V, Tripodi A, Reber G, Rand JH, Ortel TL, Galli M et al. Update of the guidelines for lupus anticoagulantdetection. Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis. J Thromb Haemost 2009;7:1737-40. Disclosure of Interest None declared