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 and results

In the DUTCH-AF registry, patients with newly diagnosed AF (<6 months) are prospectively enrolled. Label adherence 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 m2, 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 m2, 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.

[Is one DOAC better than another?]

Real-world evidence is accumulating to support the idea that there are differences among the direct oral anticoagulants (DOACs). The results of the study, discussed elsewhere in the NTvG, add to the growing body of evidence that while there is almost no difference in efficacy in prevention of the thromboembolic complications of non-valvular atrial fibrillation there are significant differences in safety. Apixaban is safer than rivaroxaban, with significantly less major bleeding, any bleeding or gastro-intestinal bleeding. Apixaban is probably the safest DOAC of the four available. These differences between DOACs with almost equal half-life are probably partly due to the differences in dosing interval: twice a day (BID) versus once a day (QD).