1. Exploring Factors Associated with Preferential Prescribing of Apixaban Over Warfarin in Patients with Non-Valvular Atrial Fibrillation
Scott McColgana, Amanj Kurdib, Jill A. Swana aNHS Ayrshire & Arran, University Hospital Crosshouse, Kilmarnock: bStrathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow
Introduction
Atrial fibrillation (AF) imparts a significantly high stroke risk for patients1. The most effective prevention of stroke in AF patients is the use of oral anticoagulant drugs2. With the advent of non-vitamin K antagonist oral anticoagulants (NOACs), no longer are clinicians and patients limited to the use of vitamin K antagonists such as warfarin. Both the prescribing rates of each oral anticoagulant and the patient group to whom each agent is being prescribed is currently unknown. Previous international studies have shown some prescribing trends but also conflicting data.
Aim & Objectives
This study further explores factors associated with prescribing apixaban over warfarin in the prophylaxis of stroke and systemic embolism in patients with NVAF including:
Patient related factors.
Disease severity using scoring tools; CHA2DS2-VASc5 and HASBLED6.
Prescribers’ characteristics and their clinical judgement.
The study also assesses whether the SAMe-TT2R27 scoring tool can predict the choice of oral anticoagulant used to evaluate its application in this patient population.
Apixaban has been selected as an alternative to warfarin in NHS Ayrshire & Arran for patients diagnosed with non-valvular atrial fibrillation (NVAF)3
NVAF = atrial fibrillation that occurs in the absence of a mechanical heart valve and in the absence of moderate to severe mitral stenosis4
Methods
Inclusion criteria; (1) have existing or newly diagnosed NVAF by electrocardiogram, (2) and be prescribed either warfarin or apixaban. Patients were excluded from the study if they were prescribed an oral anticoagulant for an indication other than NVAF. Patients were recruited using the Hospital Electronic Prescribing and Medicines Administration (HEPMA) system and review of the patients’ medical notes then determined eligibility according to the inclusion criteria. The study was conducted over 8 weeks from 3rd April – 26th May 2017 within 3 wards at University Hospital Crosshouse; the acute stroke unit and 2 care of the elderly wards.
Results
Rates of warfarin prescribing on the decline as the use of apixaban increases.
All patients newly commenced on oral anticoagulation were prescribed apixaban.
Warfarin switched to apixaban for approximately ⅙ of patients (majority post stroke/transient ischaemic attack).
SAMe-TT2R2 score correctly predicted approximately ⅓ of prescribing decisions.
Statistically significant association between the prescribing of warfarin and the presence of heart disease (excluding NVAF) was revealed (p=0.023).
CHA2DS2-VASc & HASBLED did not appear to be influential.
Older patients more likely to be prescribed apixaban.
Higher use of apixaban by Stroke specialty.
Higher use of warfarin by Care of the Elderly specialty.
Conclusion
Prescribing of apixaban rising as the use of warfarin declines with some prescribing trends evident. An additional study, with a larger sample size, is required to further assess factors associated with the selection between oral anticoagulant agents.
References: 1) Hankley GJ. Stroke. Lancet 2017;389:641–654. 2) Potpara TS et al. Novel Oral Anticoagulants in Non-Valvular Atrial Fibrillation. Best Practice & Research Clinical Haematology 2013;26: ) Gemmil J et al. Guidelines on the choice of an oral anticoagulant in patients with Non-Valvular Atrial Fibrillation (NVAF). Area Drug & Therapeutics Committee; NHS Ayrshire & Arran ) Kirchhof P et al. ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS. European Heart Journal 2016;37: ) Camm AJ et al. Guidelines for the Management of Atrial Fibrillation. European Heart Journal 2010;31: ) Pisters R et al. A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation: The euro heart survey. Chest 2010;138: ) Abumuaileq RRY et al. Evaluation of SAMe-TT2R2 risk score for predicting the quality of anticoagulation control in a real-world cohort of patients with non-valvular atrial fibrillation on vitamin-K antagonists. Europace 2015;17: