Table 1.

Methods of measuring adherence

Methods	Data source	Definition
Indirect measurements used in research and administrative settings
MPR*	Pharmacy claims	= (total days supplied)/(number of days between the first and last refills)
PDC*	Pharmacy claims	= (total days supplied)/(number of days in refill interval)
Indirect measurements used in patient care settings
Self-report	Patient	Patient recalls medications taken in response to care team query
Questionnaire	Provider	Use of validated tool for adherence markers
Pill counting	Provider	Staff member reviews patient supply for doses remaining
Dose counting device	Device	Device includes electronic or manual counter that tracks doses released
Electronic-prescribing	PBM interface	Reports transmitted from a pharmacy benefit manager to provider usually via EMR link
Direct measurement
Direct observation	Provider	Patient receives and takes medication at health care facility
Drug levels and markers	Laboratory	Patient blood or urine sample tested

Note:

^*Generally not used in direct patient care.

Abbreviations: MPR, medication possession ratio; PDC, proportion of days covered; PBM, pharmacy benefit manager; EMR, electronic medical records.