(140) Accuracy and Validity of Reported Opioid Prescription Days' Supply

Publication Number: 471

Background: Prescription days’ supply is infrequently specified by the prescriber and often calculated by the dispensing pharmacist based on prescribed quantity and directions prior to submission to third party payers and/or state prescription drug monitoring programs (PDMPs). This calculated days’ supply is commonly used in pharmacoepidemiologic opioid-related research as an outcome or exposure. While commonly used, no studies have assessed the accuracy of pharmacist-calculated days’ supply in this context.

Objectives: The main objective of this study was to estimate the percentage of opioid analgesic (OA) prescriptions dispensed by Kentucky independent pharmacies that had correctly entered days’ supply in the state PDMP system in 2019.

Methods: Using a two-stage cluster design, 25 independently owned pharmacies in Kentucky were sampled with probabilities proportional to the volume of dispensed OAs; 100 random OA prescriptions were sampled from PDMP records submitted by each pharmacy. Thirteen pharmacies were recruited and compensated $500 for participation. Following recruitment, demographic information and hard-copy prescription data for sampled records were abstracted on-site from participating pharmacies. Days’ supply was independently calculated by two pharmacist researchers using a standard formula with disagreements adjudicated blindly by a third pharmacist. Final calculated days’ supply was then compared with that submitted by the pharmacists to the PDMP. Descriptive and bivariate statistics were used to characterize the sample and assess for differences in accuracy among prescription- and practice-related factors.

Results: A total of 1300 OA prescriptions were reviewed at 13 participating pharmacies. The estimated accuracy for dispensed 2019 OA prescriptions was 89.85%, 95% CI (86.90, 92.80). This estimated accuracy varied by type of OA, with accuracy for long-acting OA prescriptions [96.00%, 95% CI (91.66, 100.00)] being significantly higher (p=0.038) than that of short-acting OA prescriptions [89.47%, 95% CI (86.30, 92.63)]. Additionally, accuracy for private pay OA prescriptions [86.1%, 95% CI (81.8, 90.3)] was found to be lower (p=0.017) compared to those billed to a third party [90.4%, 95% CI (87.3, 93.5)].

Conclusions: Overall accuracy of opioid days’ supply reported to the state PDMP was found to be moderately high. Factors such as dispensed OA type and payer source were, however, found to impact accuracy of reported days’ supply. Future studies utilizing OA days’ supply should account for factors such as these in analysis and interpretation of results.