1. What Is PDC (Proportion of Days Covered)?

PDC (Proportion of Days Covered) is a standard metric used to measure medication adherence. It calculates the percentage of days in a specified period that a patient had medication available based on prescription fill dates and days supply.

2. How Does the Calculator Work?

The calculator uses the PDC formula:

Where:

• Covered Days — Number of days the patient had medication available
• Total Days — Total number of days in the measurement period

Explanation: PDC is expressed as a percentage, with higher values indicating better medication adherence. A PDC of 80% or higher is generally considered good adherence for most chronic medications.

3. Importance of Medication Adherence Measurement

Details: Measuring medication adherence is crucial for evaluating treatment effectiveness, identifying non-adherence issues, improving health outcomes, and reducing healthcare costs. PDC is widely used by healthcare providers, insurers, and researchers to assess medication-taking behavior.

4. Using the Calculator

Tips: Enter the number of days the patient had medication available (covered days) and the total days in the measurement period. Covered days cannot exceed total days, and both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is considered good medication adherence?
A: Generally, a PDC of 80% or higher is considered good adherence for most chronic medications, though specific thresholds may vary by medication and condition.

Q2: How is PDC different from MPR (Medication Possession Ratio)?
A: While both measure adherence, PDC is generally preferred as it accounts for overlapping medication supplies and provides a more conservative estimate of adherence.

Q3: What time period should be used for PDC calculation?
A: PDC is typically calculated over a specific measurement period, often 6 or 12 months for chronic medications, but can be adapted to different timeframes as needed.

Q4: How are covered days determined?
A: Covered days are calculated based on prescription fill dates and days supply, accounting for medication overlaps and gaps in therapy.

Q5: What factors can affect PDC calculations?
A: Early refills, medication changes, hospitalizations, and prescription switching can all impact PDC calculations and should be considered when interpreting results.