Background: The prospective, randomized, open, blinded endpoint evaluation (PROBE) design has been proposed as a valid alternative to the double-blind (DB) design for trials comparing new oral anticoagulants (NOAs) with INR-adjusted vitamin K antagonists in patients with non-valvular atrial fibrillation (NVAF). Objectives: To determine whether the observed treatment effects of NOAs in patients with NVAF differ between PROBE/open-label trials and DB trials.