Background. The antiphospholipid antibody syndrome (APS) is an autoimmune disorder in which venous and arterial thrombosis or foetal loss may occur in patients with antiphospholipid antibodies (APA). The optimal intensity of oral anticoagulant (OA) therapy for the prevention of thromboembolism in patients with APS is controversial. The aim of this study was to assess the efficacy of anticoagulation with a targeted International Normalized Ratio (INR) of 2.0-3.0 for secondary prevention of thrombosis in patients with APS.
Material and methods. The patient group consisted of 21 patients (9 women and 12 men, aged 14–67, mean 33.9 ± 17.1 years) with APS. Twenty one patients (14 women and 7 men, aged 26-54, mean 44.4 ± ± 9.7 years) with inherited thrombophilia formed the reference group. APS patients and reference groupsubjects received oral anticoagulants (acenocoumarol) (targeted INR = 2.0–3.0) to prevent recurrence of thromboembolism. The INR was determined with rabbit brain thromboplastin reagent (Biomed-WSS, Warsaw) and Behring Thromborel S thromboplastin reagent. Prothrombin fragment 1+2 (F1+2) levels were measured using an enzyme-linked immunosorbent assay method (Behring).
Results. Prevention of recurrent thrombosis with acenocoumarol was followed-up in 21 patients with APS for 3–8 years (95 patient-years) and in 21 patients with inherited thrombophilia for 2–5 years (86 patientyears). Only in one APS patient a single recurrence of deep venous thrombosis was recorded (the patient decided to stop taking acenocoumarol). During acenocoumarol treatment, 3 minor bleeding episodes were observed, which did not require the interruption of anticoagulation. None of the reference group-subjects had either recurrence of thromboembolism or bleeding complication. In 10 patients with APS, as well as in 10 with inherited thrombophilia receiving acenocoumarol for prevention of recurrent thrombosis, F1+2 levels were within the normal range over a 16-week observation period.
Conclusions. Our current results indicate that oral anticoagulant therapy with a targeted INR of 2.0–3.0 prevents recurrences of venous and/or arterial thrombosis in patients with antiphospholipid antibody syndrome and carries no significant risk of hemorrhagic complications.