Number needed to treat for net effect of anticoagulation in atrial fibrillation: Real-world vs. clinical-trial evidence.

Aims: The net benefit of oral anticoagulants (OACs) in atrial fibrillation (AF) is poorly understood. We aimed to determine the NNT for net effect (NNT _net ) using calculator of absolute stroke risk (CARS) in anticoagulated patients with AF in real-world and clinical trial cohorts.
Methods: Post-hoc analysis of patient-level data from the real-world Murcia AF Project and AMADEUS clinical trial. Baseline risk of stroke was determined using CARS. The risk of stroke and major bleeding events with OAC were determined using the number of respective events at 1-year. NNT _net was calculated as a reciprocal of the net effect of absolute risk reduction with OAC (NNT _net  = 1/(absolute risk reduction of stroke[ARR _stroke ] - absolute risk increase of major bleeding[ARI _bleeding ])).
Results: In total, 3511 patients were included (1306 [37.2%] real-world patients and 2205 [62.8%] clinical trial participants). The absolute 1-year stroke risk was similar across both cohorts. In the real-world cohort, OAC was associated with a 4.0% ARR _stroke , 25 NNT _benefit , 1.0% ARI _bleeding , 100 NNT _harm and 34 NNT _net . In the clinical trial cohort, OAC was associated with a 3.8% ARR _stroke , 27 NNT _benefit , 1.6% ARI _bleeding , 63 NNT _harm and 46 NNT _net . In both cohorts, the NNT _net was significantly lower in patients with an excess stroke risk of ≥2% by CARS.
Conclusion: Overall, the NNT _net approach in AF incorporates information regarding baseline risk of stroke and major bleeding, and relative effects of OAC with the potential to include multiple additional outcomes and weighting of events based on their perceived effects by individual patients.
(© 2021 British Pharmacological Society.)