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Does co-payment for inhaler devices affect therapy adherence and disease outcomes? A historical, matched cohort study

Authors Voorham J, Vrijens B, van Boven JFM, Ryan D, Miravitlles M, Law LM, Price DB

Received 18 January 2017

Accepted for publication 7 March 2017

Published 18 April 2017 Volume 2017:8 Pages 31—41

DOI https://doi.org/10.2147/POR.S132658

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Akshita Wason

Peer reviewer comments 2

Editor who approved publication: Dr John Haughney


Jaco Voorham,1 Bernard Vrijens,2 Job FM van Boven,3,4 Dermot Ryan,5 Marc Miravitlles,6 Lisa M Law,1 David B Price1,7

1Observational & Pragmatic Research Institute Pte Ltd, Singapore, Singapore; 2Department of Public Health Sciences, Faculty of Medicine, University of Liège, Liège, Belgium; 3Unit of PharmacoEpidemiology and PharmacoEconomics, Department of Pharmacy, 4Department of General Practice, Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; 5Allergy and Respiratory Research Group, University of Edinburgh, Edinburgh, UK, 6Department of Pulmonology, Hospital Universitari Vall d’Hebron, Barcelona, Catalonia, Spain; 7Academic Primary Care, The Institute of Applied Health Sciences, University of Aberdeen, Aberdeen, UK

Background: Adherence to asthma and chronic obstructive pulmonary disease (COPD) treatment has been shown to depend on patient-level factors, such as disease severity, and medication-level factors, such as complexity. However, little is known about the impact of prescription charges – a factor at the health care system level. This study used real-life data to investigate whether co-payment affects adherence (implementation and persistence) and disease outcomes in patients with asthma or COPD.
Methods:
A matched, historical cohort study was carried out using two UK primary care databases. The exposure was co-payment for prescriptions, which is required for most patients in England but not in Scotland. Two comparison cohorts were formed: one comprising patients registered at general practices in England and the other comprising patients registered in Scotland. Patients aged 20–59 years with asthma, or 40–59 years with COPD, who were initiated on fluticasone propionate/salmeterol xinafoate, were included, matched to patients in the opposite cohort, and followed up for 1 year following fluticasone propionate/salmeterol xinafoate initiation. The primary outcome was good adherence, defined as medication possession ratio ≥80%, and was analyzed using conditional logistic regression. Secondary outcomes included exacerbation rate.
Results:
There were 1,640 patients in the payment cohort, ie, England (1,378 patients with asthma and 262 patients with COPD) and 619 patients in the no-payment cohort, ie, Scotland (512 patients with asthma and 107 patients with COPD). The proportion of patients with good adherence was 34.3% and 34.9% in the payment and no-payment cohorts, respectively, across both disease groups. In a multivariable model, no difference in odds of good adherence was found between the cohorts (odds ratio, 1.04; 95% confidence interval, 0.85–1.27). There was also no difference in exacerbation rate.
Conclusion: There was no difference in adherence between matched patients registered in England and Scotland, suggesting that prescription charges do not have an impact on adherence to treatment.

Keywords: implementation, adherence, asthma, chronic obstructive pulmonary disease, prescriptions, co-payment

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