Background/Purpose:  Acute deep vein thrombosis (DVT) is generally treated with anticoagulants for 3 to 6 months. Antiphospholipid syndrome (APS) is an important cause of DVT. However, APS can be diagnosed only 24 weeks after DVT according to the current APS classification criteria.¹ Thus, undiagnosed APS patients, who cease anticoagulant therapy after 3 months, might be exposed to a greater risk for recurrent thromboembolic event. Studies evaluating the significance of positive antiphospholipid antibody (aPL) test immediately after acute DVT are lacking. Our aim was to evaluate whether positive aPL test at the time of acute DVT diagnosis is predictive of APS.

Methods:  Patients with acute DVT, confirmed by compression ultrasound, were included into a 24-month prospective study. All patients were given anticoagulants according to the current DVT treatment guidelines. Anticardiolipin antibodies (aCL) and anti–beta2-glycoprotein I antibodies (anti- β2GPI) were determined first 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 4 weeks after anticoagulation therapy had been stopped. aCL IgG/IgM and anti-β2GPI IgG/IgM/IgA antibodies were determined by our in-house ELISA.²

Results: 157 patients (91 male, 66 female, age 52.6 ±15.8) who were included in the study had aPL titer assessed at least 5 times. 20 patients ultimately fulfilled APS classification criteria. Among these, 15/20 (75%) patients had medium or high titer aPL, 4 of whom had multiple positive aPL, already at the time of acute DVT, 2/20 (10%) had low positive aCL IgG and 1/20 (5%) had low titer aCL IgM. 2/20 (10%) were negative for aPL, but had later fulfilled APS criteria due to positive LA. APS was not established in 137/157 (87.3%) patients. Among these, 114/137 (83.2%) patients were negative for aPL at inclusion, while 2/137 (1.5%) had low titer aCL IgM and 21/137 (15.3%) had low titer aCL IgG. Altogether, diagnostically important aCL IgG/IgM and/or anti- β2GPI titer at the time of acute DVT had 93.7% specificity and 75% sensitivity for APS. Isolated low titer aCL IgG were not more frequent in patients with APS than in patients without APS (P=0.059, χ²). Completely negative aCL IgG/IgM aCL and anti-β2GPI at the time of acute DVT had a negative predictive value of 98.3%.

Conclusion:  Here we show that in patients with acute DVT positive medium or high titer aCL IgG/IgM or anti-β2GPI is suggestive of APS. These patients should therefore continue with anticoagulant therapy beyond the initial 3 to 6 months required for DVT. Our results also indicate that patients with negative aPL at the time of acute DVT do not need further aPL testing; however, LA should be determined. Low aPL titer at the time of acute DVT deems further testing imperative. References: 1. Miyakis S et al.Thromb Haemost 2006; 4: 295–306.2. 2. Cucnik S, et al. Clin Chem Lab Med 2000; 38: 777-783.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-predictive-value-of-acl-and-anti-%ce%b22gpi-in-patients-with-acute-deep-vein-thrombosis/