A randomized clinical trial of oral anticoagulant therapy in patients with the antiphospholipid syndrome: the WAPS study

Abstract number: OC365

Finazzi^* G., Marchioli† R., Barbui^* T.

†Consorzio Mario Negri Sud, S. Maria Imbaro, Italy ^*Divisione di Ematologia, Ospedali Riuniti, Bergamo, Italy;

The Warfarin in the AntiPhospholipid Syndrome (WAPS) study is a multicenter randomized clinical trial with two objectives: to compare high-dose warfarin (PT INR 3.0–4.0) vs. conventional treatment (warfarin with PT INR 2.0–3.0 for venous and aspirin for arterial thrombosis) in patients with the antiphospholipid syndrome; (b) to evaluate the clinical outcome of nonrandomized patients in a parallel observational arm of the study. A total of 462 consecutive patients (M/F 127/335; median age 39 years, range 15–83) with lupus anticoagulant or moderate to high titers of anticardiolipin antibodies have been enrolled. Of these, 109 (24%) were eligible for randomization, whereas 353 (76%) were included in the observational arm because of: asintomaticity (146, 41%), excessive bleeding risk (25, 7%), absolute need for high-dose warfarin (57, 16%), patient's unwillingness to participate (97, 27%) or other exclusion criteria (28, 8%). Median follow-up in both groups was 36 months (range 0–63). Actual PT INR of the 109 randomized patients was assessed at 3, 6, 12, 24 and 36 months. Median PT INR values of patients randomized in the high-dose group (n = 54) was 3.1, 3.2, 3.1, 3.3 and 3.3, whereas in the conventional group (n = 55) was 2.3, 2.5, 2.6, 2.5 and 2.5, respectively. A preliminary analysis of the main end points of the study was carried out in the total population, divided into randomized (n = 109) and observational (n = 353) patients. All cause mortality (4.6% vs. 3.4%) and thrombotic events (8.3% vs. 11.3%) were similar between the two groups. However, both major (4.6% vs. 0.8%, P = 0.0206) and total bleeding (22% vs. 7.4%, P < 0.0001) were significantly more frequent in the randomized patients. The final analysis of results in the two randomized arms of the study is currently ongoing and will be presented.