Last week, IHTSDO held their main annual business meeting and SNOMED CT Expo in Wellington, New Zealand. I attended, along with a number of other key players from the FHIR terminology community, and we took advantage of the opportunity to hold a joint meeting between the FHIR community and the IHTSDO community.

From the FHIR community’s point of view, this was an important meeting because many of the FHIR stakeholders make extensive use of SNOMED CT and we still have a long way to go before we’ve truly mastered all the issues associated with using SNOMED CT. From IHTSDO’s point of view, FHIR is a very important implementation mechanism by which SNOMED CT content is used in production, and their stake holders have identified working well with FHIR as a priority.

The joint meeting was split into 2 parts – a general exploration of the known issues, and a technical exploration of some of them. During those 2 meetings, we discussed the following issues:

• Progress since Montreal. In the HL7 working meeting in Montreal (May 2016), the HL7 Vocabulary WG (on behalf of IHTSDO) asked the FHIR project to make several changes around the way the FHIR Publication tools handle SNOMED CT editions, versions, copyright statements, and mappings. These were almost all completed prior to the the Wellington meeting, but we’ve been unable to transition fully to the International Edition for the base FHIR specification because of some specific value sets using US specific content. We agreed that we will change to the International Edition once this content has been promoted to the International Edition.
• Terminology Service Implementation Guide for SCT. The Terminology service API published as part of FHIR has a very active community, and we’ve been testing the API with SNOMED CT content since we first started using it (it’s already in production in Australia). However our work has primarily focused on the API, and there’s an opportunity for us to improve the service for consumers by being more consistent in how SNOMED CT structures and semantics are exposed through the API. To that end, it was recommended that HL7 and IHTSDO should collaborate on a set of detailed rules about how the SNOMED CT concepts are exposed on the terminology servers. Most of these are things that the server providers have already discussed and agreed on informally, but it would be useful to get formally documented agreement around this. IHTSDO will also look at the feasibility of providing a reference FHIR terminology server.
• Versioning – IHTSDO is planning to move towards a more continuous release cycle. While the details of this aren’t worked out yet, it may present some issues to the way we use SNOMED CT in FHIR – though FHIR is not special in this regard: all users will have the same challenges and opportunities. We agree that we will have to consider the impact this would have on the FHIR eco-system
• Cross-Edition support – Presently, the SNOMED CT implementation space is divided by the national release center system – many affiliates have their own edition, with additional concepts, descriptions, relationships, and reference sets. As long as all records come from within the same jurisdiction, this is ok, because you just choose an edition. But if your records cross jurisdictions – which is something that will happen for many systems implementing patient focused record support, then there is currently no specific guidance to support this. IHTSDO agreed that this is something that implementers will need.
• Value set review – IHTSDO has performed a review of a number of SNOMED CT value sets in the FHIR specification and provided feedback to HL7 on the results. IHTSDO has also developed a reproducible review process that may be applied to other SNOMED CT value sets. It was agreed that the review of SNOMED CT value sets in the FHIR specification should be completed, and that additional SNOMED CT value sets may be identified. IHTSDO has also previously offered to provide HL7 international with a set of SNOMED CT concepts that may be used for free in its international products. Part of the value set review will include looking at opportunities where this might be useful for the FHIR specification.
• Binding/Mapping progress / Implementation Advice – Linda Bird from IHTSDO has been working on bindings and mappings (both words are used slightly differently across IHTSDO and HL7) between SNOMED CT and FHIR resources, both a simple attribute mapping, and a more complete template binding. So far, we’ve looked at Condition, AllergyIntolerance, Observation, Procedure, Goal and Family Member History. This has identified a number of issues in terms of gaps between the relevant SNOMED CT concepts and the design of the FHIR resources. Some of these may be flaws in the FHIR resources, or in the SNOMED CT content, or they may just be inevitable results of different perspectives – that’s yet to be resolved. We need to work on this jointly, and that might lead to changes to either FHIR or SNOMED CT, or implementation guidance for FHIR implementers that use SNOMED CT, or a formal FHIR Implementation Guide. We’re not sure where that will end up yet.
• Simplification – we also discussed an idea for providing a framework for sharing additional views on SNOMED CT as a way for helping implementers. We agreed to pursue ideas around making SNOMED CT easier to use for beginning implementers informally for now. The draft SNOMED CT Machine Readable Concept Model (MRCM) currently out for community review (http://snomed.org/mrcm) may allow these simplified views to be created automatically.

A small group of IHTSDO and HL7 participants has been selected to form a joint project group to turn all these ideas into a working project plan. We’d welcome further comment from people who are interested in this area who weren’t at the joint meeting. On the HL7 side, contact me. For the IHTSDO perspective, contact Jane Millar. We’ll be working on this over the next few months.