Acute kidney injury (AKI) has been associated with use of oral anticoagulants (OACs) in patients with non-valvular atrial fibrillation (NVAF). We aimed to compare AKI risk among users of rivaroxaban vs. warfarin. We identified two cohorts of NVAF patients who initiated rivaroxaban (15/20 mg/day, N=6436) or warfarin (N=7129) excluding those without estimated glomerular filtration rate values recorded in the year before OAC initiation and those with a history of end-stage renal disease or AKI. We used two methods to define AKI during follow-up (mean 2.5 years): coded entries (method A), and the Aberdeen AKI phenotyping algorithm (method B), using recorded renal function laboratory values during the study period to identify a sudden renal deterioration event. Cox regression was used to calculate hazard ratios (HRs) for AKI with rivaroxaban vs. warfarin use, adjusted for confounders. The number of identified incident AKI cases was 249 (method) A and 723 (method B). Of the latter, 104 (14.4%) were also identified by method A. After adjusting for age, sex, baseline renal function and comorbidity, HRs (95% CIs) for AKI were 1.20 (0.93–1.55; p =0.16) using method A, and 0.80 (0.68–0.93; p <0.01) using method B. Estimates stratified by baseline level of chronic kidney disease were largely consistent with the main estimates. In conclusion, our results support a beneficial effect of rivaroxaban over warfarin in terms of AKI occurrence in patients with NVAF. More research into how best to define AKI using primary care records would be valuable for future studies.

A Gonzalez-Perez, ME Saez and LA Garcia Rodriguez work for CEIFE, which has received research funding from Bayer AG. LA Garcia Rodriguez has also received honoraria for serving on advisory boards for Bayer AG. Y Balabanova is an employee of Bayer AG. G Brobert was an employee of Bayer AB at the time of the study and is currently a paid consultant for Bayer.

AG-P, LAGR and MES work for CEIFE, which received research funding from Bayer AG for this work. YB is an employee of Bayer AG, and GB is a former employee of Bayer and current consultant for Bayer. Both YB and GB contributed to the study design, review of manuscript drafts and decision to publish.

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NHS Multi-centre Research Ethics Committee gave ethical approval for this work

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The data underlying the results presented in the study are available from A Gonzalez-Perez (the corresponding author) agonzalez@ceife.es