Oral anticoagulation use by patients with atrial fibrillation in Germany

Atrial fibrillation (AF) is the most common significant cardiac rhythm disorder. Oral anticoagulation (OAC) is recommended by guidelines in the presence of a moderate to high risk of stroke. Based on an analysis of claims-based data, the aim of this contribution is to quantify the stroke-risk dependent OAC utilisation profile of German AF patients as well as the possible causes and the associated clinical outcomes of OAC under-use. Our data set was derived from two large mandatory German medical insurance funds. Risk stratification of patients was based on the CHADS2-score and the CHA2DS2-VASc-score. Two different scenarios were constructed to deal with factors potentially disfavouring OAC use. Causes of OAC under-use and its clinical consequences were analysed using multivariate analysis. Observation year was 2008. A total of 183,448 AF patients met the inclusion criteria. This represents an AF prevalence of 2.21%. The average CHADS2-score was 2.8 (CHA2DS2-VASc-score: 4.3). On between 40.5 and 48.7% of the observed patient-days, there was no antithrombotic protection by OAC, other anticoagulants or aspirin. Older female patients with a high number of comorbidities had a higher risk of OAC under-use. Patients who had already experienced a thromboembolic event had a lower risk of OAC under-use. In the observation year, 3,367 patients experienced a stroke (incidence rate 1.8%). In our multi-level Poisson random effects estimate, OAC use decreases the stroke rate by almost 80% (IRR 0.236). In conclusion, OAC under-use is widespread in the German market. It is associated with severe clinical consequences.