SAT0441 Predictive value of antiphospholipid antibodies in the acute phase of deep vein thrombosis
Authors: K. Perdan Pirkmajer, A. Boc, S. Čučnik, A. Mavri, P. Žigon, E. Podovšovnik, M. Štalc, N. Vene, A. Ambrožič
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Deep vein thrombosis (DVT) is frequent and potentially life threatening disease with tendency to reoccur. Anticoagulant treatment of the first episode of DVT usually lasts 3 months. Antiphospholipid syndrome (APS) is an important cause of DVT. However, the APS can be confirmed only 24 weeks after DVT according to the current APS classification criteria.<sup>1</sup> Thus, undiagnosed APS patients, who cease anticoagulant therapy after 3 months, might be exposed to a greater risk for recurrent venous thromboembolism. Studies evaluating the significance of positive antiphospholipid antibody (aPL) test in the acute phase of DVT are lacking. <h3>Objectives</h3> To evaluate whether positive aPL test at the time of acute DVT diagnosis is predictive of APS. <h3>Methods</h3> Patients with acute DVT were included into a 24 month prospective study. All patients were given anticoagulants. aCL IgG/IgM and anti-β2GPI IgG/IgM/IgA antibodies were determined by our in-house ELISA<sup>2</sup> at inclusion and then every 4 weeks for the first 24 weeks. The last aPL measurement was performed 24 months after inclusion into the study. APS was confirmed if a patient tested positive (medium or high positive aCL and/or presence of anti-β2GPI) 12 and 24 weeks after DVT. Lupus anticoagulants (LA) were tested after cessation of anticoagulation. <h3>Results</h3> 196 patients (111 male, 85 female, age 54±2 years) included in the study had aPL titer assessed at least 5 times. Ultimately, 20/196 (10.2%) patients fulfilled APS classification criteria. Among these, 15/20 (75%) patients had medium or high titer aPL at the time of acute DVT (1 of them had double positive aPL and 2 of them had multiple positive aPL at first aPL determination). Two patients (10%) had low positive aCL IgG and one had low titer aCL IgM. Two patients (10%) were negative for aPL, but had later fulfilled APS criteria due to positive LA. APS was not established in 176/196 (89.8%) patients. Among these, 146/176 (83%) patients were negative for aPL at inclusion, while 30/176 (17%) had low titer aCL IgM or aCL IgG. Altogether, diagnostically important aCL IgG/IgM and/or anti- β2GPI titer at the time of acute DVT had 83% specificity and 90.5% sensitivity for APS. Isolated low titer aCL IgG were more frequent in patients with APS than in patients without APS (χ2=125.6; p&lt;0.001). Completely negative aCL IgG/IgM and anti-β2GPI in the acute phase of DVT had a negative predictive value of 98.6%. <h3>Conclusions</h3> Here we show that in acute phase of DVT, positive medium or high titer aCL IgG/IgM or anti-β2GPI is suggestive of APS. In these patients continuation of anticoagulation beyond the initial 3 months should be considered. Patients with negative aPL in the acute phase of DVT do not need further aPL testing; however, LA should be determined. Low aPL titre at the time of acute DVT deems further testing imperative. <h3>References</h3> [1] Miyakis S, et al.Thromb Haemost2006;4:295–306.2. [2] Cucnik S, et al. Clin Chem Lab Med2000;38:777–783. <h3>Disclosure of Interest</h3> None declared