Search of MEDLINE (1966 to November 2005) and Cochrane Library electronic databases (2005) and reference lists for randomized trials, meta-analyses of randomized trials, and prospective cohort studies of the treatment of
thrombosis risk in patients with
antiphospholipid antibodies or APS. Studies were selected on the basis of clinical relevance.
EVIDENCE SYNTHESIS: Among patients with
antiphospholipid antibodies, the absolute risk of developing new
thrombosis is low (<1% per year) in otherwise healthy patients without prior thrombotic events, may be moderately increased (up to 10% per year) in women with recurrent fetal loss without prior
thrombosis, and is highest (>10% in the first year) in patients with a history of
venous thrombosis who have discontinued
anticoagulant drugs within 6 months. Compared with placebo or untreated control, anticoagulation with moderate-intensity
warfarin (adjusted to a target international normalized ratio [INR] of 2.0-3.0) reduces the risk of recurrent
venous thrombosis by 80% to 90% irrespective of the presence of
antiphospholipid antibodies and may be effective for preventing recurrent arterial
thrombosis. No evidence exists that high-intensity
warfarin (target INR, >3.0) is more effective than moderate-intensity
warfarin. For patients with a single positive
antiphospholipid antibody test result and prior
stroke,
aspirin and moderate-intensity
warfarin appear equally effective for preventing recurrent
stroke. Treatment issues that have not been addressed in clinical trials, or for which the evidence is conflicting, include the role of antithrombotic prophylaxis in patients with
antiphospholipid antibodies without prior
thrombosis, the optimal treatment of noncerebrovascular arterial
thrombosis, recurrent
thrombosis despite
warfarin therapy, and treatment of women with
antiphospholipid antibodies and recurrent fetal loss.
CONCLUSIONS: In patients with APS, moderate-intensity
warfarin is effective for preventing recurrent
venous thrombosis and perhaps also arterial
thrombosis.
Aspirin appears to be as effective as moderate-intensity
warfarin for preventing recurrent
stroke in patients with prior
stroke and a single positive test result for
antiphospholipid antibody. The optimal treatment of other thrombotic aspects of APS needs to be addressed in well-designed prospective studies.