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Mapping HL7v2 messages to FHIR.

Publication date: Apr 13, 2015

Recently I wrote a new whitepaper about how one would map HL7v2 messages to FHIR, which can be a challenge.

Recently I wrote a new whitepaper about how one would map HL7v2 messages to FHIR. This was inspired by the new testing track for the upcoming FHIR connectathon in Paris (May 2015). Working on the whitepaper also forced me to have a good look at the current (DSTU 2, up for ballot right now) version of the FHIR specification.

As you probably know FHIR supports a RESTful exchange of resources, as well as the document and messaging interoperability paradigm. Of these the messaging paradigm is probably the least documented option. Given that commonly used interoperability standards such as HL7 version 2 and even DICOM are messaging based we should be able to populate a FHIR resource repository with data derived from HL7 v2 messages.

There are two ways to do a transformation:

  • Assume that the FHIR server supports the massaging paradigm. In that case one can simply translate the HL7v2 message into a FHIR message, whereby the FHIR message consists of a bundle consisting of the MessageHeader resource (with support for sender/receiver and trigger event) and other resources such as Patient, Encounter, Observation and AllergyIntolerance. This mapping (for ORU messages) turned out to be relatively straightforward, see section 2 of the whitepaper. (Note however that none of the known FHIR Server implementations currently supports messaging).
  • Assume that the FHIR server only supports REST (probably a realistic assumption for the near future). This means that some "TransformationAgent" (e.g. an interface engine/communication server) will not just have to map the data from HL7v2 segments to FHIR resources, it will also have to bridge the messaging-REST paradigms. The latter aspect is quite challenging, see section 3 of the whitepaper.

In the context of a FHIR server that only support REST:

  • With 'declarative' style messaging (broadcast stuff like ADT and ORU) it's easy to support the v2-messsage-to-REST transformation in an integration engine. We'll focus on this use-case during the Paris connectathon, in the full knowledge that orders and queries are much more tricky (we'll try and deal with those at a subsequent connectathon).
  • Handling 'orders' (ORM) will be tricky indeed, because of the need for workflow control, and the need to create things like 'application acknowledgements'. We may need a FHIR WorkList type of resource to support this, maybe along the lines of the IHE XDW Workflow document.
  • With queries there may be issues around the v2 query continuation protocol, and the different way in which the result sets are created - at the time of the initial query (in v2) or dynamically (in FHIR). If using an interface engine this could implicate that a) engine receives v2 query which requests e.g. max. 5 results, b) engine sends query to FHIR server for all matches c) engine persists result set in local storage c) engine creates query result message based on local storage, and creates results message for any v2 continuation queries it receives.

This issue will need more thought - at least two parties have expressed a willingness to test this in Paris - that should help to move things forward. In the meantime, I've found a series of issues in the FHIR publication, which (how oldfashioned..) I've added to a balloting spreadsheet.

This week I'll be heading for Berlin, to attend a mhealth BarCamp held during the ConHIT trade show - with all the HIMSS stuff going on this week one would almost forget that there are other events taking place as well. I hope to see you there, I'll be talking about FHIR.


PS: We'll be offering (for the first time ever) a FHIR Advanced training course on May 28th in London.

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