To the Editor We appreciate the interesting study by Hernandez et al1 on the risk of bleeding with dabigatran in patients with atrial fibrillation. These are important data to an ongoing controversy. However, we would appreciate an author comment regarding the external validity of the study. To what extent is this sample of Medicare beneficiaries representative of the general population of patients with atrial fibrillation? Comparing the characteristics of patients in the RE-LY Study2 and the Danish population-based study,3 it seems that these are not effortlessly comparable. In the study by Hernandez et al,1 patients are considerably older (average age, 76 years) than patients in the RE-LY study or the Danish study (average ages, 72 and 70 years, respectively). Notably, the frequency of coadministration of antiplatelet drugs was 8% in the current study compared with 40% in both the RE-LY and the Danish population data. From the distribution of CHADS2 (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, prior stroke or transient ischemic attack or thromboembolism) scores across these studies, it seems that a substantial proportion of Medicare recipients are at lower risk than those reported in the other 2 articles.
Henriksen DP, Hansen MR, Damkier P. Patient Characteristics and Risk of Bleeding With Dabigatran in Atrial Fibrillation. JAMA Intern Med. 2015;175(7):1245. doi:10.1001/jamainternmed.2015.1289
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