Estimated medical cost reductions associated with apixaban in real-world patients with non-valvular atrial fibrillation.

Objective: The Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation (ARISTOTLE) trial demonstrated that apixaban was effective in reducing the risk of stroke and major bleeding in non-valvular atrial fibrillation (NVAF) patients. Medical cost avoidance studies for oral anticoagulants have used warfarin event rates from clinical trials, which may not reflect the real-world (RW) setting. This study aimed to estimate the difference in medical costs associated with apixaban instead of warfarin in RW NVAF patients.

Methods: This study selected patients with NVAF diagnosis during 2007-2010 from a Medco population of US commercial and Medicare health plans. Stroke and major bleeding excluding intracranial hemorrhage (MBEIH) were identified using diagnosis codes. Pharmacy claims were used to define warfarin exposure periods. Rates of stroke and MBEIH were calculated during warfarin exposure. To estimate the absolute risk reduction (ARR) between warfarin and apixaban in RW, the relative risk reductions (RRR) from ARISTOTLE were multiplied by the event rates observed in RW during warfarin exposure. Medical cost reductions associated with apixaban were calculated by applying the ARR to the 1-year incremental cost for each event. Stroke and MBEIH costs were obtained from the literature and adjusted to 2011 levels.

Results: During a patient year, the use of apixaban instead of warfarin resulted in medical cost reductions of $493 for stroke and $752 for MBEIH and $1245 for the combined outcome of both events. The medical costs avoided were greater as baseline stroke risk increased.

Conclusion: If RRRs demonstrated in ARISTOTLE persist in RW, the use of apixaban will be associated with lower medical costs vs warfarin. Main limitations of this study were: identification of clinical events using administrative codes rather than confirmatory clinical data, inability to evaluate the level of international normalized ratio (INR) control, and not including INR monitoring and drug costs.