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Curr Med Res Opin. 2019 Mar 29:1. doi: 10.1080/03007995.2019.1601944. [Epub ahead of print]

Improving the accuracy of medication adherence measures using linked prescription and dispensation data: findings from the ESOSVAL cohort of patients treated with osteoporosis drugs.

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a Health Services Research Unit , Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO) , Valencia , Spain.
b Spanish Network for Health Services Research in Chronic Care - Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC).
c Primary Care Centre of Nazaret District , Valencia , Spain.



We compare estimates of Proportion of Days Covered (PDC) based on dispensation-only data versus linked prescription and dispensation information, and we analyse their differences in a real-world cohort of patients with osteoporosis.


Prospective cohort study. We compared four alternative measures of PDC, using dispensation-only data: a) with a fixed assessment interval and b) censoring the assessment interval at the moment of the last refill, and using linked prescription and dispensation data: c) considering a minimum prescription gap of three months to interpret interruption by the physician and d) considering any prescription gap.


The mean PDC at 12 months for new users was 63.1% using dispensation-only data and a fixed interval, 86.0% using dispensation-only data and a last-refill interval, 81% using linked dispensation and prescription data and censoring any period without prescription, and 78.3% when using linked prescription and dispensation data and censoring periods of at least 3 months. For experienced users, the figures were 80.0%, 88.9%, 83% and 81%, respectively. Overall, dispensation-based measures presented issues of patient misclassification.


Linked prescription and dispensation data allows for more precise PDC estimates than dispensation-only data, as both primary non-adherence and early non-adherence periods, and fully non-adherent patients, are all identified and accounted for.


Proportion of Days Covered; dispensation data; medication adherence; methods; prescription data; real-world data

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