How is the proportion of days covered (PDC) calculated?

The proportion of days covered (PDC) is a key metric used to assess medication adherence and is calculated by determining the number of days a patient has medication available during a specified time interval. This method effectively reflects how well a patient follows their prescribed medication regimen over time.

In this case, calculating PDC involves taking the total number of days that the medication is on hand—considering refills, overlaps, and proper medication usage—then comparing that figure to a specific time frame over which the adherence is being measured. The resulting figure is expressed as a percentage, providing insight into the extent of adherence.

This approach specifically addresses the days the medication is available rather than simply measuring prescriptions or doctor visits, making it a more practical measure for understanding patient compliance with their treatment plan. The focus is on how many days in a given period the patient had access to their medication, which is critical for chronic disease management and assessing overall health outcomes.