Determinants of label non-adherence to non-vitamin K oral anticoagulants in patients with newly diagnosed atrial fibrillation

Aims To evaluate the extent and determinants of off-label non-vitamin K oral anticoagulant (NOAC) dosing in newly diagnosed Dutch AF patients. Methods In the DUTCH-AF registry, patients with newly diagnosed AF (,6 months) are prospectively enrolled. Label adherence and results to NOAC dosing was assessed using the European Medicines Agency labelling. Factors associated with off-label dosing were explored by multivariable logistic regression analyses. From July 2018 to November 2020, 4500 patients were registered. The mean age was 69.6 + 10.5 years, and 41.5% were female. Of the 3252 patients in which NOAC label adherence could be assessed, underdosing and overdosing were observed in 4.2% and 2.4%, respectively. In 2916 (89.7%) patients with a full-dose NOAC recommendation, 4.6% were underdosed, with a similar distribution between NOACs. Independent determinants (with 95% confidence interval) were higher age [odds ratio (OR): 1.01 per year, 1.01–1.02], lower renal function (OR: 0.96 per ml/min/1.73 m ², 0.92–0.98), lower weight (OR: 0.98 per kg, 0.97–1.00), active malignancy (OR: 2.46, 1.19–5.09), anaemia (OR: 1.73, 1.08–2.76), and concomitant use of antiplatelets (OR: 4.93, 2.57–9.46). In the 336 (10.3%) patients with a reduced dose NOAC recommendation, 22.9% were overdosed, most often with rivaroxaban. Independent determinants were lower age (OR: 0.92 per year, 0.88–0.96) and lower renal function (OR: 0.98 per ml/min/1.73 m ², 0.96–1.00). Conclusion In newly diagnosed Dutch AF patients, off-label dosing of NOACs was seen in only 6.6% of patients, most often underdosing. In this study, determinants of off-label dosing were age, renal function, weight, anaemia, active malignancy, and concomitant use of antiplatelets.