Primary medication nonadherence calculation method specifications impact resulting rates.

Background: Previous literature has illustrated a wide range of primary medication nonadherence (PMN) rates due to inconsistent calculation methods and parameters, but the impact of parameter specifications on PMN rates has not been assessed.

Objectives: The objective of this study was to evaluate the impact of lookback window (LBW), duplicate window (DW), and fill window (FW) specifications on PMN rates in patients prescribed specialty self-administered oncology medications.

Methods: This was a single-center, retrospective cohort analysis.