Thromboembolic risk in patients with high titre anticardiolipin and multiple antiphospholipid antibodies

Asymptomatic antiphospholipid antibody (aPL) carriers with high risk for thrombosis may benefit from preventive anticoagulation. It was our objective to test whether the risk of thrombosis increases with: 1) increasing titres of anticardiolipin antibodies (aCL) after adjustment for other cardiovascular risk factors and 2) the number of aPL detected. In a cross-sectional study, blood was collected from clinics in two teaching hospitals. The study included 208 individuals suspected of having an aPL and 208 age- and sex-matched controls having blood drawn for a complete blood count. Clinical variables included history of previous arterial (ATE) or venous (VTE) thrombotic events, traditional risk factors for cardiovascular disease, and systemic lupus erythematosus (SLE). Laboratory variables included IgG/IgM aCL, lupus anticoagulant, and IgG/IgM anti-beta2-glycoprotein 1. Mean age was 46.5 years and 83% were female. Seventy-five of the 416 participants had greater than or equal to 1 aPL, and 69 had confirmed greater than or equal to 1 ATE or VTE. Family history was positive in 48% of participants, smoking in 28%, hypertension in 16%, diabetes in 6%, and SLE in 20%. A 10-unit increase in aCL IgG titre was associated with an odds ratio (OR) [95% CI] of 1.07 [1.01-1.13] for ATE and 1.06 [1.02 - 1.11] for VTE. The odds of a previous thrombosis increased with each additional aPL detected: 1.5 [0.93-2.3] for ATE and 1.7 [1.1-2.5] for VTE. These results indicate that increased titres of aCL and multiple aPL were associated with an increased risk of a previous thrombotic event.