OBJECTIVES: In routine clinical practice the selection of a particular anticoagulant for treatment of a specific patient may be based on a variety of different factors. The aim of this study was to explore if there were differences in the characteristics of patients with non-valvular atrial fibrillation (NVAF) who started on dabigatran etexilate (DE) and who in the prior year had no oral anticoagulant treatment (initiators) versus those who had previously been treated with warfarin (switchers). METHODS: Medco claims data were used to characterize 7,055 NVAF patients from the US with a DE prescription between Feb 2011 and Apr 2012. The first prescription in this period defined the index date. The treatment-groups were stratified by initiators and switchers. Characteristics, comedications, and comorbidities in the 12-month-period prior to index date were assessed. All illustrated differences were statistically significant (p <0.05) (1) RESULTS: Switchers (N = 2,585) had a mean age of 74.0 (±9.6) years, whereas initiators (N=1,903) were younger (mean 70.0 (±9.6) years). A higher proportion of switchers used comedications compared to initiators, e.g. beta blockers (66% vs. 59%), and gastrointestinal drugs (34% vs. 28%). Switchers were more likely to have congestive heart failure, hypertension, cerebrovascular disease, renal disease and bleeding related hospitalizations when compared to the initiators, and also had a higher mean CHADS-VASc score (4.0 (±1.8) compared to initiators (3.4 (±1.9)). CONCLUSIONS: This study shows differences between patients who are initiating DE as first anticoagulant treatment and those who are switched from warfarin to DE revealing that switchers might represent a distinct patient population. Identifying, stratifying or accounting for such differences are necessary in comparisons using real world data. (1) Schoof N et al., Characteristics of patients with non-valvular atrial fibrillation using dabigatran or warfarin in the US. Curr Med Res Opin. 2013 Dec 27