Improving the accuracy of medication adherence measures using linked prescription and dispensation data: findings from the ESOSVAL cohort of patients treated with osteoporosis drugs.
Curr Med Res Opin. 2019 Mar 29;:1 Authors: García-Sempere A, Hurtado I, Sanfélix-Genovés J, Rodríguez-Bernal C, Peiró S, Sanfélix-Gimeno G
OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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. PMID: 30924690 [PubMed - as supplied by publisher]