What is the primary role of the Master Patient Index (MPI) in Epic?

• A. To store medical imaging data
• B. To manage user access permissions
• C. To assign a unique identity to each patient across the system
• D. To track inventory in the pharmacy

Answer: (C)

The main idea is that the Master Patient Index provides a single, unique identity for each patient across the entire Epic system. It creates and maintains one patient identifier that links every piece of data—appointments, encounters, labs, notes, billing, and more—so that all records referring to the same person come together as a cohesive, accurate record. This unified identity helps prevent duplicates and mismatches, ensuring clinicians see the complete, correct history for a patient no matter where in the system the data originated.

Imaging storage isn’t handled by the MPI (that’s the job of imaging systems like PACS), and security or access controls aren’t managed by the MPI (those are about who can log in and what they can do). Inventory tracking for the pharmacy is another separate function.