Is the Currently Used Prescription Adjudication Date a Good Proxy for Calculating Medication Refill Adherence?

BACKGROUND: The Centers for Medicare & Medicaid Services (CMS) adopted the proportion of days covered (PDC) calculation for use in their Five-Star Quality Rating System for Medicare Advantage and Prescription Drug Plans. This calculation uses the prescription adjudication date (i.e., date the prescription is billed to the benefits manager by a pharmacy) as a proxy for medication adherence. Adherence programs, such as automatic refill programs, have become commonplace in community pharmacy and have been identified by industry leaders as interfering with the ability to accurately measure adherence using PDC. OBJECTIVE: To evaluate the prescription pickup date instead of the currently used adjudication date to calculate PDC in the presence of a community pharmacy automatic refill program. METHODS: This study used a post-only quasi-experimental design with patients aged 65 years or older enrolled in automatic and manual refill programs in a 29-store community pharmacy chain during 2014. PDC was calculated using the prescription adjudication date and pickup date (i.e., date the patient brought the medication home) using pharmacy dispensing data for CMS adherence metrics medications, including statins, renin angiotensin aldosterone system antagonists (RASA), and noninsulin diabetes medications. Mann-Whitney U and effect size calculations evaluated differences in PDC between automatic and manual refill prescriptions for the adjudication date and pickup date, as well as the difference in PDC between adjudication and pickup date. RESULTS: 10,936 prescriptions were included with 21.9% enrolled in the automatic refill program. Mean (SD) adherence was 88.6 (17.6) and 86.4 (17.1) for automatic refills and 85.8 (19.0) and 85.0 (18.9) for manual refills, using the adjudication date and pickup date PDC, respectively. Significant difference existed between automatic and manual refill prescriptions using the adjudication date (P < 0.001) but not for the pickup date. The difference between adjudication and pickup date PDC ranged from 0% to 32.0% for automatic refills and 0% to 38.7% for manual refills. The difference between adjudication and pickup date PDC was significant when comparing automatic and manual refill prescriptions (P < 0.001). CONCLUSIONS: The artificial inflation seen with adjudication date PDC indicates that the prescription pickup date is a more accurate reflection of patient medication taking. Automatic refills resulted in a less reliable PDC compared with manual refill prescriptions. Discussion about the continued use of the adjudication date to calculate PDC is needed.