Comparison of treatment effect estimates of non-vitamin K antagonist oral anticoagulants versus warfarin between observational studies using propensity score methods and randomized controlled trials

Emerging observational studies using propensity score (PS) methods assessed real-world comparative effectiveness of non-vitamin K antagonist oral anticoagulants (NOACs) versus warfarin in patients with non-valvular atrial fibrillation (AF). We aimed to compare treatment effect estimates of NOACs between PS studies and randomized controlled trials (RCTs). Electronic databases and conference proceedings were searched systematically. Primary outcomes included stroke or systemic embolism (SE) and major bleeding. A random-effects meta-analysis was performed to synthesize the data by pooling the PS- and RCT-derived hazard ratios (HRs) separately. The ratio of HRs (RHR) from the ratio of PS-derived HRs relative to RCT-derived HRs was used to determine whether there was a difference between estimates from PS studies and RCTs. There were 10 PS studies and 5 RCTs included for analysis. No significant difference of treatment effect estimates between the PS studies and RCTs was observed: RHR 1.11, 95 % CI 0.98-1.23 for stroke or SE; RHR 1.07, 95 % CI 0.87-1.34 for major bleeding. A significant association between NOACs and risk of stroke or SE was observed: HR 0.88, 95 % CI 0.83-0.94 for the PS studies; HR 0.79, 95 % CI 0.72-0.87 for the RCTs. However, no relationship between NOACs and risk of major bleeding was found: HR 0.91, 95 % CI 0.79-1.05 for the PS studies; HR 0.85, 95 % CI 0.73-1.00 for the RCTs. In this study, treatment effect estimates of NOACs versus warfarin in patients with non-valvular AF from PS studies are found to be in agreement with those from RCTs.