Use of Direct Oral Anticoagulants in Canadian Primary Care Practice 2010–2015: A Cohort Study From the Canadian Primary Care Sentinel Surveillance Network

BACKGROUND As questions have been raised about the appropriateness of direct oral anticoagulant (DOAC) dosing among outpatients with atrial fibrillation, we examined this issue in patients being managed by primary care providers. METHODS AND RESULTS This was a retrospective cohort new-user study using electronic medical records from 744 Canadian primary care clinicians. Potentially inappropriate DOAC prescribing was defined as prescribing lower or higher doses than those recommended by guidelines for patients with nonvalvular atrial fibrillation. Of the 6658 patients with nonvalvular atrial fibrillation who were prescribed a DOAC (mean age: 74.8; 55% male), 626 (9.4%) had a CHADS2 score of 0, and 168 (2.5%) had a CHADS-VASc score of 0. Of the DOAC prescriptions, 527 (7.7%) were deemed potentially inappropriate: 496 (7.2%) were potentially underdosed, and 31 (0.5%) were prescribed a dose that was higher than recommended. Patients were more likely to be prescribed lower-than-recommended doses if they were female (adjusted odds ratio [aOR]: 1.3 [95% confidence interval (CI), 1.0-1.5]), had multiple comorbidities (aOR: 1.4 [95% CI, 1.1-1.8])-particularly heart failure (aOR: 1.6 [95% CI, 1.2-2.0]) or dementia (aOR: 1.4 [95% CI, 1.1-1.8])-or if they were also taking aspirin (aOR: 1.7 [95% CI, 1.3-2.1]) or nonsteroidal anti-inflammatory drugs (aOR: 1.2 [95% CI, 1.02-1.5]). Potentially inappropriate DOAC dosing was more common in rural practices (aOR: 2.1 [95% CI, 1.7-2.6]) or smaller practices (aOR: 1.9 [95% CI, 1.6-2.4] for practices smaller than median). CONCLUSIONS The vast majority of DOAC prescriptions in our cohort of primary care-managed patients appeared to be for appropriate doses, particularly since prescribing a reduced dose of DOAC may be appropriate in frail patients or those taking other medications that predispose to bleeding.