IgA anti-β2-glycoprotein I as an independent risk factor in acute venous thromboembolism.

Background: Venous thromboembolism (VTE) is the third most common cause of cardiovascular death. Primary Antiphospholipid Syndrome (P-APS) is a chronic systemic autoimmune disorder characterized by thrombotic events and/or obstetric complications in patients carrying antiphospholipid antibodies (aPL) without autoimmune pathology. The prevalence of primary antiphospholipid syndrome (P-APS) in patients with VTE is approximately 9%. However, few studies have evaluated non-criteria antiphospholipid antibodies in the acute phase of VTE. Objective: To assess the role of criteria and non-criteria antiphospholipid antibodies in patients with acute VTE. Methods: A cohort of 181 patients with VTE was followed for 2 years. An age-matched control group of 181 healthy individuals was included for comparison. Results: Criteria aPL were detected in 8.8% of patients, whereas non-criteria aPL were present in 23.8%. Criteria aPL were independently associated with overall VTE (OR 7.09, p=0.021) and unprovoked VTE (OR 4.61, p=0.021). IgA anti-Beta2 Glycoprotein-1 antibodies (aB2GP1), detected in 16% of patients, were independently associated with VTE (OR 4.31, p=0.014) and unprovoked VTE (OR 3.78, p=0.006). Furthermore, IgA aB2GP1 positivity was also associated with more severe clinical presentation, defined by a Pulmonary Embolism Severity Index scale ≥3 (OR 3.13; p=0.048), and with the development of chronic thromboembolic pulmonary hypertension (OR 5.7; p=0.008). Conclusion: IgA aB2GP1 antibodies are independently associated with VTE, particularly unprovoked VTE, and with both severe pulmonary embolism, and subsequent chronic thromboembolic pulmonary hypertension.