April 16, 2015
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Stroke and bleeding risks, prescription benefits, impact anticoagulant selection

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Patients with nonvalvular atrial fibrillation who have increased ischemic stroke risk and bleeding were more likely to initiate warfarin therapy, according to research published in The American Journal of Cardiology.

However, generous prescription benefit coverage strongly predicted the use of novel oral anticoagulants and drove medication selection, researchers from the University of North Carolina at Chapel Hill found.

“In this large study of patients with AF initiating anticoagulation, we found strong associations between ischemic stroke risk, bleeding risk, and prescription benefits generosity and anticoagulant selection,” the researchers wrote.

Julie C. Lauffenburger, PharmD, PhD, of the divisions of pharmaceutical outcomes and policy, and colleagues from other departments extracted a cohort of 70,498 patients with nonvalvular AF initiating anticoagulation from a U.S. database of commercial and Medicare supplement claims (October 2010-December 2012).

The investigators set out to determine how stroke risk prediction, bleeding risk and prescription benefit coverage impacted anticoagulant usage.

Multivariable regression was used to examine the relationships between the risk of ischemic stroke (CHA2DS2-VASc score), bleeding (Anticoagulation and Risk Factors in Atrial Fibrillation [ATRIA] score) and prescription benefit generosity (proportion of patient-covered costs relative to total costs) with warfarin and novel oral anticoagulant (NOAC) selection, as well as with the option of dabigatran (Pradaxa, Boehringer Ingelheim) and rivaroxaban (Xarelto, Janssen Pharmaceuticals).

Models were adjusted for patient baseline characteristics not included in the clinical prediction risk scores. Dabigatran was used by 29.9% of patients and rivaroxaban by 7.9% of patients. To assess variation, the researchers utilized C-statistics and partial chi-square statistics.

Compared with warfarin, patients were less likely to receive a NOAC with increased ischemic stroke risk (CHA2DS2-VASc ≥ 2; adjusted RR = 0.75; 95% CI, 0.72-0.77) and elevated bleeding risk (ATRIA ≥ 5; aRR = 0.66; 95% CI, 0.64-0.69); the likelihood was higher with good benefits generosity (≤ 20% patient-covered costs; aRR = 2.03; 95% CI, 1.92-2.16).

Prescription benefits generosity explained nearly twice the model variation as either ischemic stroke or bleeding risk score.

Patients with high bleeding risk were more likely to have rivaroxaban prescriptions filled (aRR = 1.16; 95% CI, 1.09-1.24) than dabigatran prescriptions.

“Our results suggest that clinicians may be differentially choosing warfarin in real-world clinical practice for patients with both high stroke risk and bleeding risk, indicating possible concerns about the lack of a reversal agent for the NOACs,” the researchers wrote. “Future research needs to continue to address this concern.” – by Allegra Tiver

Disclosure: Lauffenburger reports funding from the National Institute of Nursing Research. Please see the full study for a list of all other authors’ relevant financial disclosures.