1. Master Patient Index (MPI) is a database used across healthcare organizations to maintain consistent and accurate demographic and medical data for each patient using a unique identifier. This helps ensure each patient is only represented once across different healthcare systems. 2. Enterprise MPI (EMPI) specifically refers to an MPI used across an entire healthcare enterprise. An EMPI provides APIs for searching and finding patient identifiers and records across different healthcare systems. It also includes a match engine to link patient records despite errors or inconsistencies in data. 3. A government white paper discusses how MPI serves as an access point linking patient identifiers to individual or aggregated patient records across facilities nationwide. It is important to ensure data quality and integrity within the MPI by

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MPI: Master Patient Index
Yuzhe Tang
Georgia Institute of Technology, GA, USA
Email:yztang@gatech.edu
GTID#: 902641656
I. A1: (OpenEMPI) Overview
Patient identity management is important in HIE (Healthcare Information Exchange); normally,
HIE happens in two steps: 1) a patient’s identity is accurately determined across the institutions
2) then it starts to share Healthcare data across organizations.
MPI aims at linking patient identity information across Healthcare providers.
MPI is difficult, because of multiple patient identifiers, semantic difference/vagueness (e.g.
patient may have multiple names.)
This articles introduces OpenEMPI, which is a high-performance open-source EMPI (Enter-
prise MPI). It is organized based on the principles of SOA (service oriented architecture).
II. Enterprise master patient index
This wiki entry describes Enterprise MPI (or MPI simply). Again, MPI is a database used
across a healthcare organization to maintain consistent and accurate demographic and medical
data of the patient. Usually a patient is assigned a unique identifier and use it to refer to this
patient across the enterprise. The goal is to ensure that each patient is represented only once
across all software within an organization.
EMPI is intended to solve the inconsistency problem in which multiple systems’ data become
inconsistent due to patient information changes (only on one of these systems).
Master (as in MPI) here means enterprise-wide scope.

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An EMPI provides API for searching and querying the index to find patients and the pointers
to their identifiers and records in the respective systems.
A key component of an EMPI is the match engine (?matching identifiers with patient’s records
in the system?). The match engine needs to handle the corner cases including typos, misspellings,
aliases and more. Due to errors in the data, match engine or MPI should also provide interface
for reviewing the results (which the engine can not definitively determine a match or not).
In the market of MPI providers, there are commercial vendors including NextGate, Atlas and
HealthUnity. There are also open-source EMPI systems, such as OpenEMPI and others.
III. Master Patient Index: Linking Quality Healthcare Across the Nation (a
government white paper)
MPI is a database with patient data populated from all facilities nationwide. It serves as an
access point linking patient identifier with individual or aggregated patient records. MPI “provide
a list of all treating facilities at which a patient has received care.”
It is necessary to ensure the overall integrity of the patient data within MPI. The data quality
includes removing duplicates and so on.