Abstract: We included data from 67,688 participants randomised into 13 RCTs. The included trials directly compared dose-adjusted warfarin with either apixaban, betrixaban, darexaban, edoxaban, idraparinux, idrabiotaparinux, or rivaroxaban. The majority of the included data (approximately 90%) was from apixaban, edoxaban, and rivaroxaban. The composite primary efficacy endpoint of all strokes (both ischaemic and haemorrhagic) and non-central nervous systemic embolic events was reported in all of the included studies. Treatment with a factor Xa inhibitor significantly decreased the number of strokes and systemic embolic events compared with dose-adjusted warfarin in participants with AF (OR 0.89, 95% CI 0.82 to 0.97; 13 studies; 67,477 participants; high-quality evidence). Treatment with a factor Xa inhibitor significantly reduced the number of major bleedings compared with warfarin (OR 0.78, 95% CI 0.73 to 0.84; 13 studies; 67,396 participants; moderate-quality evidence). There was, however, statistically significant and high heterogeneity (I2 = 83%). When we repeated this analysis using a random-effects model, it did not show a statistically significant decrease in the number of major bleedings (OR 0.88, 95% CI 0.66 to 1.17). A pre-specified sensitivity analysis excluding all open-label studies showed that treatment with a factor Xa inhibitor significantly reduced the number of major bleedings compared with warfarin (OR 0.75, 95% CI 0.69 to 0.81), but high heterogeneity was also observed in this analysis (I2 = 72%). The same sensitivity analysis using a random-effects model also showed a statistically significant decrease in the number of major bleedings in participants treated with factor Xa inhibitors (OR 0.76, 95% CI 0.60 to 0.96). Treatment with a factor Xa inhibitor significantly reduced the risk of intracranial haemorrhages (ICHs) compared with warfarin (OR 0.50, 95% CI 0.42 to 0.59; 12 studies; 66,259 participants; high-quality evidence). We observed moderate, but statistically significant heterogeneity (I2 = 55%). The pre-specified sensitivity analysis excluding open-label studies showed that treatment with a factor Xa inhibitor significantly reduced the number of ICHs compared with warfarin (OR 0.47, 95% CI 0.40 to 0.56), with low, non-statistically significant heterogeneity (I2 = 27%). Treatment with a factor Xa inhibitor also significantly reduced the number of all-cause deaths compared with warfarin (OR 0.89, 95% 0.83 to 0.95; 10 studies; 65,624 participants; moderate-quality evidence). Treatment with factor Xa inhibitors significantly reduced the number of strokes and systemic embolic events compared with warfarin in people with AF. The absolute effect of factor Xa inhibitors compared with warfarin treatment was, however, rather small. Factor Xa inhibitors also reduced the number of ICHs, all-cause deaths and major bleedings compared with warfarin, although the evidence for a reduction in the latter is less robust.

Plain-language summary: We searched various sources up to 29 August 2017 and included 13 studies that involved 67,688 people with atrial fibrillation who received either a factor Xa inhibitor or a vitamin K antagonist. All included people were adults and on average aged between 65 and 74 years. Approximately one-third were women. We found that factor Xa inhibitors when compared with warfarin, which was used as comparator in all trials, reduced the number of strokes in people with atrial fibrillation. This reduction was, however, rather small. Factor Xa inhibitors also appeared to reduce the number of serious bleedings (including those into the brain) and the number of people dying from any cause compared with warfarin. We considered the quality of evidence in our review as moderate to high. The studies that we included were generally large to very large. We found that the results from the larger studies were generally similar and this strengthened our findings. Finally, we are confident that we included all relevant studies in our review and did not miss any important studies.