When non-vitamin K antagonist (VKA) oral anticoagulants (NOACs) are prescribed by Canadian primary care physicians (PCPs) and specialists for non-valvular atrial fibrillation (NVAF), data has suggested that lower doses are commonly used. We aimed to: (1) identify the proportion on CCS AF Guideline-recommended OAC; (2) estimate the rate of NOAC dosing that is lower- and higher-than-recommended; and, (3) understand the reasons why patients receive reduced NOAC doses. The OPTIMAL AF Program is an ethically approved, national, observational, knowledge translation, quality enhancement initiative where PCPs and specialists are undertaking a chart audit of their anticoagulated NVAF (i.e., excluding mechanical heart valve, rheumatic mitral stenosis) patients (≥18 years age, without severe renal dysfunction) through either an electronic medical record (EMR) system (Telus Health Platforms/Practice Solutions/Med Access) or standardized, paper-based data collection forms. As of April 5, 2018, 1512 patients (EMR n=965, paper-based n=547) from 95 physician practices (84 PCPs, 11 specialists) in eight provinces are included. The median age is 77 (25th, 75th percentiles: 70, 83) years; 89% are ≥65 years; 38% are female; 11% have a body weight ≤60 kg; the median CHADS2 score is 2 (1, 3) and CHA2DS2-VASc is score 4 (3, 5); and (as most recently reported by local laboratory) the median eGFR was 61 (50, 74) ml/min/1.73 m2. By inclusion criterion, all patients are receiving OAC: 16% of patients receive warfarin, 52% of whom have their most recent INR in the 2-3 range. 84% are on NOAC: apixaban 49%, rivaroxaban 34%, dabigatran 17%, edoxaban <1%. Standard dose NOAC is used in 77% (see Figure). When comparing NOAC dose with Health Canada prescribing recommendations, we observed apparent lower-than-recommended dosing in 41% of patients on reduced dose (i.e., 9% of the overall NOAC cohort) and higher-than-recommended dosing in 5% on standard dose (i.e., 4% overall). Among patients on reduced dose NOAC that was discordant with prescribing recommendations, physicians provided reason(s) (see Table). More than eight in 10 NVAF Canadian patients in our study are receiving NOAC for stroke prevention as per CCS AF Guideline recommendations. However, among warfarin-treated patients there is suboptimal INR control in ∼50%. Despite relatively infrequent apparent lower-than-recommended dosing (∼one in 11 patients) and higher-than-recommended dosing (∼one in 26 patients) of NOAC, opportunities remain to further minimize the discordance between product monograph-based prescribing recommendations and NOAC dosing used in routine clinical practice.View Large Image Figure ViewerDownload Hi-res image Download (PPT)
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