Objective To evaluate warfarin prescription, quality of international normalised ratio (INR) monitoring and of INR control in patients with atrial fibrillation (AF) and chronic kidney disease (CKD).
Methods We performed a retrospective cohort study of patients with newly diagnosed AF in the Veterans Administration (VA) healthcare system. We evaluated anticoagulation prescription, INR monitoring intensity and time in and outside INR therapeutic range (TTR) stratified by CKD.
Results Of 123 188 patients with newly diagnosed AF, use of warfarin decreased with increasing severity of CKD (57.2%–46.4%), although it was higher among patients on dialysis (62.3%). Although INR monitoring intensity was similar across CKD strata, the proportion with TTR≥60% decreased with CKD severity, with only 21% of patients on dialysis achieving TTR≥60%. After multivariate adjustment, the magnitude of TTR reduction increased with CKD severity. Patients on dialysis had the highest time markedly out of range with INR <1.5 or >3.5 (30%); 12% of INR time was >3.5, and low TTR persisted for up to 3 years.
Conclusions There is a wide variation in anticoagulation prescription based on CKD severity. Patients with moderate-to-severe CKD, including dialysis, have substantially reduced TTR, despite comparable INR monitoring intensity. These findings have implications for more intensive warfarin management strategies in CKD or alternative therapies such as direct oral anticoagulants.
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Contributors All of the authors had a substantial role in the planning, data acquisition, analysis and/or writing of the manuscript.
Funding MPT is supported by a Veterans Health Services Research & Development Career Development Award (CDA09027-1), an American Heart Association National Scientist Development Grant (09SDG2250647), Gilead Sciences Cardiovascular Scholars Award and a VA Health Services and Development MERIT Award (IIR 09-092). WCW's work on this project was supported through NIH grant R01DK095024. The content and opinions expressed are solely the responsibility of the authors and do not necessarily represent the views or policies of the Department of Veterans Affairs.
Competing interests None declared.
Ethics approval Stanford Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.