• Min Jun, Matthew T James, Zhihai Ma, Jianguo Zhang, Marcello Tonelli, Finlay A McAlister, Braden J Manns, Pietro Ravani, Robert R Quinn, Natasha Wiebe, Vlado Perkovic, Stephen B Wilton, Wolfgang C Winkelmayer, Brenda R Hemmelgarn, and Alberta Kidney Disease Network.
• Cumming School of Medicine, Division of Nephrology, University of Calgary, Alberta, Canada; The George Institute for Global Health, The University of Sydney, Sydney, Australia.
• Am. J. Kidney Dis. 2017 Jun 1; 69 (6): 734-743.

BackgroundThe effectiveness and safety of warfarin use among patients with atrial fibrillation (AF) and reduced kidney function are uncertain.Study DesignCommunity-based retrospective cohort study (May 1, 2003, to March 31, 2012) using province-wide laboratory and administrative data in Alberta, Canada.Setting & Participants14,892 adults 66 years or older with new AF and a measurement of kidney function. Long-term dialysis patients or kidney transplant recipients were excluded.PredictorPropensity scores were used to construct a matched-pairs cohort of patients with AF who did and did not have a warfarin prescription within a 60-day period surrounding their AF diagnosis.OutcomesWithin 1 year of initiating warfarin therapy (or the matched date for nonusers): (1) the composite of all-cause death, ischemic stroke, or transient ischemic attack (also assessed as separate end points) and (2) first hospitalization or emergency department visit for a major bleeding episode defined as an intracranial, upper or lower gastrointestinal, or other bleeding.MeasurementsBaseline glomerular filtration rate (GFR) was estimated using the CKD-EPI creatinine equation. Patients were matched within estimated GFR (eGFR) categories: ≥90, 60 to 89, 45 to 59, 30 to 44, and <30mL/min/1.73m2. Information for baseline characteristics (sociodemographics, comorbid conditions, and prescription drug use) was obtained.ResultsAcross eGFR categories, warfarin therapy initiation was associated with lower risk for the composite outcome compared to nonuse (adjusted HRs [95% CI] for eGFR categories ≥ 90, 60-89, 45-59, 30-44, and <30mL/min/1.73m2: 0.59 [0.35-1.01], 0.61 [0.54-0.70], 0.55 [0.47-0.65], 0.54 [0.44-0.67], and 0.64 [0.47-0.87] mL/min/1.73m2, respectively). Compared to nonuse, warfarin therapy was not associated with higher risk for major bleeding except for those with eGFRs of 60 to 89mL/min/1.73m2 (HR, 1.36; 95% CI, 1.13-1.64).LimitationsSelection bias.ConclusionsAmong older adults with AF, warfarin therapy initiation was associated with a significantly lower 1-year risk for the composite outcome across all strata of kidney function. The risk for major bleeding associated with warfarin use was increased only among those with eGFRs of 60 to 89mL/min/1.73m2.Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

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