In reading a recent debate on the HL7 strucdoc list, I saw the term “post-coordinate” but didn’t know what it meant. Post-coordinate is a SNOMED CT term for a piece of clinical text that requires more than one code or attribute to explain it. Of course, the term predates SNOMED CT and is used in controlled vocabulary circles to indicate cases where a set of codes is used to explain a single concept because the vocabulary doesn’t have a single code for that concept yet.
What they are talking about on the mailing list is whether a coding block for some text can use multiple codes to describe the text. In HL7, the Concept Descriptor (CD) type allows a “qualifier: LIST<CR>” attribute for this purpose. The Coded with Equivalents (CE) type is a restricted form of CD that does not include “qualifier.” The Data Types – Abstract Specification includes this example:
<value code="128045006" codeSystem="SNOMED-CT" displayName="cellulitis (disorder)">
<qualifier code="56459004" displayName="foot structure">
<name code="363698007" displayName="finding site"/>
</qualifier>
</value>
So, why not use CD all the time? The problem is that it’s more difficult for a database or search program to compare a multi-valued field than a single-valued one. I’d be interested in seeing papers discussing methods for comparing multi-coded SNOMED CT values to each other.
Tags: SNOMED · vocabulary1 Comment
Thank You