Feature Friday - Embedded Master Patient Index

In our Feature Friday series this time I'll discuss another great feature of the Founda Health platform that allows you to register and link different identifiers (a.k.a. Medical Record Numbers) for a patient. This functionality referenced as "X-Ref" is part of the XDS registry inside our platform, and can be activated through configuration.

First some "MPI" theory

In a Health Information Exchange setting it is inevitable that the same (human) patient is identified with different "medical record numbers" within different healthcare organisations. This poses a challenge when exchanging patient information between healthcare organisations since external patients must be reconciled to local ones before such information can be used reliably.

In more abstract terms the problem is that multiple patient identity sources create and maintain different patient identities for the same human/person. In a healthcare setting the patient identity source is often the EHR, or a departmental system. Identifiers are the "numbers" by which patients are uniquely identified within these systems. The challenge therefor comes down to linking patient identities in such a way that it is understood which patient identifiers refer to the same human/person.

Please note the subtle difference between patient identifiers and patient identities. The latter refer to the digital equivalent of a real patient created by a system. The First refer to the "numbers" associated with these identities in order to uniquely identify them in a system.

This is where the Master Patient Index system come into the picture. MPIs exist to discover patient identities that refer to the same (human) patient, and manage the links between them. The logical approach of many MPIs has been to create a "global" or "master" patient identity to which other patient identities are linked based on MPI specific matching algorithms.

The IHE Patient Information Cross-reference (PIX) profile was created to allow applications to interact with an MPI system to (1) feed it with patient identity information, and (2) discover linked identities. The Founda Health Platform X-Ref functionality implements a PIX Manager actor.

How does it work

Within the XDS Registry of the Founda Health Platform patient identities are created for each patient identity source that is connected. During initial setup a patient identity source (for example, the hospital's EMR) is associated with one or more "assigning authorities" of which one is defined (via configuration) as the global or master identifier. As a result each patient identity is associated with one or more identifiers that are stored as HL7v2 ADT messages are received from the patient identity source. As each ADT message carries one or more patient identifiers in its PID.3 segment, identifiers that are recognised are stored and linked through the X-Ref functionality inside the Founda Health platform.

PIX Manager

In a "classic" XDS Affinity Domain a Registry is associated with only one assigning authority as agreed upon by the network participants. This is referred to as the "global patient identifier". The consequence of this is that each XDS document source actor must replace a local patient identifier with the corresponding global patient identifier prior to submitting a document to the XDS network.

This is where the X-Ref functionality comes into play. When enabled it keeps track of the various local patient identifiers and link these to the global identifier. XDS Sources and Consumer systems can then discover and use these links using IHE PIX transactions (ITI-9 or ITI-45) supported by our platform.

Question then remains how identifiers are linked to the same identity?

Manually linking patient identifiers

When using the Founda Health platform viewer there is the possibility to link multiple identifiers to a patient identity through the "Additional Patient Identifiers" widget on the "Patient Details" tab.

Depending on configuration discussed above the "Add additional identifier" drop down will show a list with pre-defined assigning authorities used in the HIE network that can be linked. A user simply selects the assigning authority that corresponds with the healthcare facility (s)he is working, enters a local patient identifier and clicks the "Add" button.

When doing so the patient details of both identities are shown to the user requesting to confirm the linking after visual validation that (s)he is indeed linking the same (human) patients.

The patient attributes shown in the dialog are as rich as the HL7 ADT messages used when registering these patient identities.

Automatically linking patient identifiers

The same linking can be achieved using HL7v2 ADT message that are sent to the X-Ref interface through an ITI-8 (Patient Identity Feed) transaction. When the ADT message contain assigning authorities that correspond with the configured assigning authorities in the Founda Health platform's XDS registry the associated patient identifiers are automatically linked.

Links can be altered or removed using HL7 ADT A24 (link) or A37 (unlink) messages.

Summary

The Founda Health platform ships with an embedded IHE PIX compatible X-Ref manager allowing an HIE network to associate multiple patient identifiers with a patient identity when the X-Ref functionality is enabled. Identifiers can be linked manually, or automatically using HL7 messages. When the enabled external document sources and/or document consumers can discover linked identifiers using IHE PIX (v2/v3) transactions.

If you like to know more about Founda Health solutions for Health Information Exchange in general, or Image Exchange in particular please check out our website or contact us for more information.