• anti-β2 glycoprotein I antibodies;
  • antiprothrombin antibodies;
  • lupus anticoagulant;
  • venous thrombosis

Summary.  We have determined lupus anticoagulants, anti-β2 glycoprotein I (β2GPI) and antiprothrombin antibodies in the Leiden Thrombophilia Study, a population-based case–control study designed to determine risk factors for deep venous thrombosis (DVT). Lupus anticoagulant (LAC) was measured in 473 patients and 472 control subjects. Four control subjects (0.9%) and 14 patients (3.1%) had a positive LAC, resulting in a 3.6-fold increased risk [odds ratio (OR) 3.6, 95% CI: 1.2–10.9]. Of the total population, 49 were positive for anti-β2GPI antibodies: 15 controls (3.4%) and 34 patients (7.5%), implying a 2.4-fold increased risk (95% CI: 1.3–4.2). Antiprothrombin antibodies were present in 114 subjects: 48 controls (11.0%) and 66 cases (14.6%) with an OR of 1.4 (95% CI: 1.0–2.1). When LAC was considered in the co-presence of antiprothrombin or anti-β2GPI antibodies the OR increased to 10.1 (95% CI: 1.3–79.8). A LAC without a positive anti-β2GPI or antiprothrombin test was not associated with a risk for DVT (OR 1.3, 95% CI: 0.3–6.0). This study demonstrates that the presence of LAC, anti-β2GPI antibodies and antiprothrombin antibodies are risk factors for DVT in a general population. The strongest association holds for the combination LAC and the presence of anti-β2GPI or antiprothrombin antibodies.