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

Jaco Voorham; Bernard Vrijens; Job Fm van Boven; Dermot Ryan; Marc Miravitlles; Lisa M Law; David B Price

doi:10.2147/POR.S132658

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

Pragmat Obs Res. 2017 Apr 18;8:31-41. doi: 10.2147/POR.S132658. eCollection 2017.

Authors

Jaco Voorham¹, Bernard Vrijens², Job Fm van Boven^{3

4}, Dermot Ryan⁵, Marc Miravitlles⁶, Lisa M Law¹, David B Price^{1

7}

Affiliations

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

Abstract

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: adherence; asthma; chronic obstructive pulmonary disease; co-payment; implementation; prescriptions.