Describes what PDC is, how it is calculated, and how it is viewed/used in the Outcomes platform.
Proportion of Days Covered (PDC)
Outcomes’ PDC aligns with CMS specifications for Medicare Star Rating Adherence Measures as developed and maintained by the Pharmacy Quality Alliance (PQA).
What is PDC?
Proportion of Days Covered (PDC) is the preferred methodology to calculate a patient’s adherence to chronic medications. A PDC of ≥80% is supported by clinical evidence and deemed the ‘adherent’ threshold for most medications, although a higher PDC may be necessary for some medications to be considered adherent (e.g. oral contraceptives, antiretrovirals).1
What are examples of Part D Patient Safety measures which leverage PDC? 2
- Medication Adherence for Diabetes Medications: % of patients whose adherence rate for diabetes medications is ≥80%
- Classes: biguanides, DPP-IV inhibitors, GLP-1 agonists (excluding products only indicated for weight loss), meglitinides, SGLT2 inhibitors, sulfonylureas, TZDs
- Patients taking insulin are excluded from this measure
- Medication Adherence for Hypertension (RAS antagonists): % of patients whose adherence rate for RAS antagonists is ≥80%
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- Patients taking Entresto (sacubitril/valsartan) are excluded from this measure
- Medication Adherence for Cholesterol (Statins): % of patients whose adherence rate for statins is ≥80%
How is PDC calculated?
PDC = (days covered) / (total days in period) x 100
How does Outcomes use PDC?
Outcomes leverages PDC, alongside other data points, to target patients for adherence services to facilitate better clinical outcomes for patients. PDC can be based upon either a pharmacy’s or a health plan’s fill history.
How can I see PDC in the Outcomes platform?
Outcomes Premium and RCS users can see patient PDC values for the 3 Star Rating Adherence Measures, as applicable, for patients with two qualifying fills within the Patient Profile in the Outcomes platform.
Adherence trend graphs, as well as your pharmacy’s fill history, can be seen for a patient after selecting an adherence measure PDC.
Outcomes users can also view PDC information for patients enrolled in the Adherence Monitoring Program (AMP) under the Patients tab, accessible from the Dashboard.
Resources:
- Pharmacy Quality Alliance. Adherence Measures. April 19, 2022. https://www.pqaalliance.org/adherence-measures
- Centers for Medicare and Medicaid Services. Medicare 2025 Part C & D Star Rating Technical Notes. October 3, 2024. https://www.cms.gov/files/document/2025-star-ratings-technical-notes.pdf