P1898Prevalence and risk of DOACs inappropriate dosing in atrial fibrillation. An analysis of the Swiss-AF and BEAT-AF registries

Abstract Background Direct oral anticoagulants (DOACs) have a similar efficacy in terms of stroke and mortality reduction as compared to Vitamin K-Antagonists (VKAs) and improved safety with regards to intracranial haemorrhage in patients with non-valvular atrial fibrillation (AF). Dose of DOACs needs to be adjusted according to age, weight, renal function and concomitant medication. Yet, off-label dosages have been reported in 11 - 45% of patients (on average 20%). Purpose To assess the prevalence of inappropriate DOAC-dosing according to the official prescribing information in two large prospective Swiss AF cohorts (Swiss-AF and BEAT-AF) and to evaluate its correlation with adverse clinical outcomes. Methods All 3267 patients taking oral anticoagulants were stratified at baseline as receiving DOACs (adequately dosed, under- or overdosed) or VKAs. Appropriateness of DOAC dosing was assessed based on age (≥80 years), weight (≤60kg) and renal function (serum creatinine ≥133μmol/l [apixaban]; creatinine clearence ≤50ml/min [all other DOACs]). Clinical outcomes were collected during a median follow-up of 2.96 years. Major adverse clinical events (MACE) consisted of a combination of myocardial infarction, cardiac death, ischemic stroke and systemic embolism. Safety was assessed by occurrence of any bleeding event. Results 1902 patients (58%) were on VKAs and 1365 on DOACs (42%). In the DOAC group, 1149 patients received a dose consistent with drug labelling (84%), 133 (10%) received an inappropriately high and 83 (6%) an inappropriately low dose. Overdosed patients were older than those adequately treated and more likely female, had a lower BMI and a higher CHA2DS2-VASc score (4 vs. 3 points) (p<0.001 for all). Underdosed patients were more likely to have concomitant antiplatelet therapy (p<0.001). Both off-label groups were more likely to have a history of coronary artery disease, heart failure and chronic kidney disease (p<0.001). Kaplan-Meier cumulative incidence rates for the first occurrence of MACE or bleedings are provided in Figure 1. Overdosed patients had an almost two-fold higher risk of bleeding (9.0 vs. 5.0 events per 100 patient-years compared to correctly dosed DOACs and to VKAs) and a higher rate of MACE (5.1 vs. 2.3 events per 100 patient years compared to correctly dosed DOACs and 5.1 vs. 3.4 compared to VKAs). Underdosing did not seem to be associated with a relevant increase in ischemic or bleeding events as compared to correctly dosed DOACs and VKAs (see Figure 1). Figure 1. Kaplan-Meier incidence curves Conclusion Inadequate DOACs dosing was found in 1 in 6 patients and correlated with a higher burden of comorbidities at baseline. Underdosing correlated with concomitant antiplatelet therapy. Overdosing was associated with adverse clinical outcome for ischemic and bleeding events.