Are the results of randomized controlled trials on anticoagulation in patients with atrial fibrillation generalizable to clinical practice?

Background: Randomized trials demonstrate a clear benefit of anticoagulation in patients with atrial fibrillation at risk of stroke, but the proportion of eligible patients who are treated with anticoagulants remains low. The reluctance to treat all eligible patients with anticoagulants may be due to studies in clinical practice showing variable risk-benefit, raising concerns about application to general medical practice. Methods: A systematic review of published medical literature was performed to identify studies of patients with atrial fibrillation who were treated with warfarin in actual clinical practice. Data from these studies were compared with pooled data from randomized controlled trials. Results: Three studies met the predefined criteria, each in a different health care setting, totaling 410 patients with 842 patient-years of follow-up. Patients in clinical practice were older and had more comorbid conditions compared with trial participants. However, the ischemic stroke rate was similar between clinical practice and randomized studies (1.8% [95% confidence interval {CI}, 0.9%-2.7%] vs 1.4% [95% CI, 0.9%-2.0%]). Intracranial hemorrhage (0.1% [95% CI, 0%-0.3%] vs 0.3% [95% CI, 0.06%-0.5%]) and major bleeding (1.1% [ 95% CI, 0.4%-1.8%] vs 1.3% [95% CI, 0.8%-1.8%]) rates were also similar. There was a higher rate of minor bleeding in clinical practice than in trials (12.0% [95% CI, 9.7%-14.3%] vs 7.9% [95% CI, 6.6%-9.2%]). Conclusions: Patients who undergo anticoagulation for atrial fibrillation in actual clinical practice differ from those in randomized trials, but have similar rates of stroke and major bleeding. The risk of minor bleeding is higher and may require more intensive monitoring in practice.