MPI and Patient Identity

Master Patient Index and Identity

The master patient index, or MPI, is the system that links a patient to health record numbers, encounters, demographic data, and other identity elements. In some organizations, the same function is called an enterprise master patient index when it spans multiple facilities or systems.

CCA Domain 3 includes retrieving patient information from the MPI. The point is not just finding a name. The coder must locate the correct patient and encounter so the right documentation supports the right codes, claim, quality data, and disclosure decisions.

Common Identity Elements

MPI data may include name, aliases, date of birth, sex, address, phone, medical record number, enterprise identifier, encounter numbers, facility, and sometimes links to prior names or merged records. Matching should use multiple identifiers, not one detail alone.

Identity Error Types

A duplicate occurs when one patient has more than one medical record number. An overlay occurs when documentation for one patient is filed under another patient's record. An overlap can occur when one patient has separate records across systems that should be linked but are not.

Duplicates can hide prior history and split coding data. Overlays can mix diagnoses, procedures, allergies, and test results between patients. These errors can affect patient safety, coding accuracy, claims, quality reporting, and privacy.

CCA Response Pattern

If a coder suspects an MPI problem, the correct answer is to stop relying on the questionable record and report the issue through the HIM or identity management process. The coder should not merge records, delete data, or keep coding from a record that may belong to a different patient unless policy authorizes the next step.

Identity management is also a data quality function. Standard naming conventions, demographic validation, registration accuracy, and duplicate review all support reliable health information.