Accuracy and validity of reported opioid prescription days' supply

The primary objective of this study was to estimate the percentage of opioid analgesic (OA) prescriptions dispensed by Kentucky independent pharmacies with correctly entered days' supply in the state prescription drug monitoring program (PDMP) system in 2019.

Using a two-stage cluster design, pharmacies were sampled with probabilities proportional to the volume of dispensed OAs; 100 random OA prescriptions were sampled from PDMP records submitted by each pharmacy. Following recruitment, demographic information and hard-copy prescription data for sampled records were abstracted on-site. Days' supply was independently calculated by two pharmacists using a standard formula with disagreements adjudicated blindly by a third pharmacist. Adjudicated days' supply was compared with that submitted to the PDMP and classified as accurate/inaccurate. Descriptive statistics were used to characterize the sample and a multivariable logistic regression model was used to assess the relationship between accuracy and prescription/practice-related factors.

A total of 1281 OA prescriptions were reviewed at 13 participating pharmacies. Accuracy of reported OA days' supply was 89.85%, (95% CI: 86.90, 92.80). Factors associated with accuracy were presence of special instructions from the prescriber (OR 3.13 [95% CI: 1.43, 6.82]), presence of 'as-needed' directions (OR 0.29 [95% CI: 0.18, 0.47]), and billing to a third-party payer (OR 1.43 [95% CI: 1.01, 2.02]).

Accuracy of OA days' supply reported to the state PDMP was found to be moderately high. Certain prescription-related factors influence accuracy and should be accounted for in future studies. Patterns, including opioid 'split-billing' were identified and may impact validity of PDMP and administrative claims studies.