Validity of the days supply field in pharmacy administrative claims data for the identification of blister packaging of medications.

While the NPV was high, the PPV for identifying blister packaging using the days supply field in pharmacy claims data was modest given the low prevalence in blister pack use. The best predictor occurred when 28 days was compared with 30 days. KEY POINTS Blister packs are arranged in 4 × 7 compartments and are often used to improve adherence, but no studies have examined whether it was possible to identify the use of blister packs using the days supply field in pharmacy claims data. Findings show that a 28-day supply yielded a high sensitivity and specificity for identifying the use of blister packaging compared with a 30-day supply, but there is potential for misclassification. Future studies directed at examining subgroups that are more likely to use blister packs and replication of findings using other data sources in other jurisdictions are encouraged.