2.10pm. Dr David Hay is the chair of the NZ HL7 users group.
SNOMED CT:
- Is a terminology
- Has a structure
- Has a grammar that allows the codes to be combined into expressions (post-coordination)
- Is used to store data in Clinical Data Systems
David showed us how SNOMED concepts are described in the CliniClue browser.
He then went on to talk about HL7 and gave us some background facts:
- Founded in 1987
- Non-Profit ANSI accredited SDO
- 2000+ members
- Meets 3 times a year to work on standards, with electronic meetings
- Mission: provide a complete framework (and related standards) for the exchange integration and retrieval of electronic health documents
David then explained how HL7 v2 messages work. There’s not much use of SNOMED in V2 although could be used anywhere in a message where the datatype is CE (Coded Entry). In v2 you can imply context if you wanted to but you need to be careful.
Next up, david explained that the main goal of HL7 v3 was to implement semantic interoperability between mulitple applications. V3 has:
- A reference model
- Refined models (R-MIM)
- Formal design methodology
- Defined vocabularies
- XML based messages and document
David then showed us the RIM:
BUT – normal people don’t need to know this!
Different people take out of the RIM what they need for their V3 messages. e.g. Patient care, Pharmacy, structured documents (e.g. CDA).
Clinical Document Architecture (CDA):
- RMIM refined from RIM
- Header and Body
- Human readable
- Supports incremental semantic interoperability
- Level 3 is where clinical data is codified in a format (Clinical Statements) that applications can interpret -> relevant to SNOMED
Key problem with CDA Clinical Statements is that they can either be implemented as SNOMED or as something else. TermInfo is an HL7 project that develops guidance for using terminologies with information models.
Summary:
- HL7 - 2 main specifications for messaging: v2 and v3
- SNOMED CT can be used in both, but v3 is preferred
- Because of overlap between SNOMED and v3, TermInfo provides recommendation for use
- In general where SNOMED CT is the vocabulary, the preference is to express clinical ideas using post-coordingation rather than HL7 attributes, but sometimes both are required.
