Applying a coherent framework to drug utilisation studies : the use of direct oral anticoagulants in patients with atrial fibrillation in Scotland

Mueller, Tanja and Alvarez-Madrazo, Samantha and Robertson, Charles and Bennie, Marion (2017) Applying a coherent framework to drug utilisation studies : the use of direct oral anticoagulants in patients with atrial fibrillation in Scotland. In: Royal Statistical Society Conference 2017, 2017-09-04 - 2017-09-07.

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Abstract

Background: Information regarding adherence to treatment with direct oral anticoagulants (DOACs) is still limited. Drug utilisation research is commonly being conducted to analyse the usage of drugs in clinical practice, but drug utilisation studies make use of a variety of conceptual definitions and a diverse set of measurements. The aim of this study was therefore two-fold: to report on DOAC use in Scotland; and to advocate the standardisation of drug utilisation methods. Methods: Retrospective cohort study using linked routinely collected administrative data. Patients include those with a diagnosis of atrial fibrillation (AF) who received a first prescription for a DOAC (dabigatran, rivaroxaban, apixaban) from September 2011 to December 2015. In order to give a valid representation of patients` drug taking behaviour, this study comprises various measures of both discontinuation/persistence and adherence. Results: 14,811 patients (mean CHA2DS2-VASc score 2.93 [SD 1.71], 87.2% with ≥ 5 concomitant medicines) were treated with DOACs for a median of 346 days (IQR 167 – 597). 41.4% discontinued treatment during the study period; however, 57.7% re-initiated DOACs, and persistence after 12 months was 80.6%. Differences between DOACs were observed: discontinuation rates ranged from 34.0% (apixaban) to 75.9% (dabigatran), and 12 months persistence from 61.8% (dabigatran) to 83.6% (apixaban). Adherence to treatment with all DOACs was good: overall DOAC median medication refill adherence (MRA) was 102.3% (IQR 90.1% - 112.5%), and 81.9% of patients had an MRA > 80%. Conclusions: In Scotland, adherence to DOAC treatment was good. However, discontinuation and persistence rates were variable – although treatment interruptions were often temporary. To decrease the inconsistencies in drug utilisation methods and facilitate meaningful study comparison, the use of a coherent framework – combining discontinuation, persistence and adherence – and the standardisation of measurements is advocated.