The system being presented is SNOMED CT.
That is SNOMED plus the Clinical Terms Thesaurus (CTT)
CTT was the later name for the Read Code version 3, or actually Read 3.1, since we[1] regarded 3.0 as no good, largely as it didn’t contain the codes and rubrics from the earlier sets – Read 4 byte and Read 5 byte (most of you are using the latter, EMIS users will remember the former, and the pain of change).
The Mayo Clinic was contracted to handle the combination of the multiaxial SNOMED set with the Read 3.1/CTT. The NHS and Treasury[4] convened a working group to advise them whether a way of determining if this work was done well could be produced. We[2] gave a clear answer. The answer was “no”, but I expect it was done adequately well.
Read/CTT is good at general practice stuff, less good at hospital stuff. SNOMED is good at pathology, and I assume much of the hospital stuff apart from that. Read/CTT already embodied – actually enveloped – the ICD and the UK extensions to ICD 9 and I presume 10[3]
The two sets have an area of overlap, where codes should be mapped onto each other, and areas that don’t overlap where the result will be that you can code a wider range of concepts with the single system.
I think it is more complex, centralised, prescriptive and unevolutionary[5] than is ideal, but that the persistent efforts to hold copyright on these collections of terms and the manner of their handling compels that. And therefore coding systems, as with natural language, should not be restrictively licenced and should be presented as Open Source or Commons.
So it has been planned all this century, or at least intended.
[1] the specialty working group for quality assurance in Clinical Terms/Read/Thesaurus. We didn’t write them, we did criticise and accept.
[2] Just after the Hammersmith train crash, and just about under the line it happened on. I was asked to attend. One member got a curious smile when I remarked the whole lot should be Open Source, because he was unable to announce that his unit at the University of Manchester were about to do just that, until the following week.
[3] it was a while ago, and I’ve not been involved (I’m not sure if any doctors have been) for quite some time.
[4] It was an effort to explain to the Treasury chap why this mattered. I think it was accomplished – two cultures and all that.
[5] as in the evolving nature of language, with loan words and so on