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From: | Rogerio Luz Coelho |
Subject: | Re: [Gnumed-devel] the WHY: Re: clinicians: coding use case survey - please respond ! |
Date: | Wed, 4 May 2011 14:25:33 -0300 |
Here's an explanation of why I am being so specific about
the coding thing:
There's fundamentally two different ways to associate codes
with narrative:
#--------------------------------------------------------------------
1) codes "stand for" (are equivalent to) certain blocks of narrative:
create table coded_term (
term text
code text
)
create table episode (
description
)
Note how
- the episode does NOT directly link to coded_term
- coded_term does NOT have unique(term, code)
With this setup
- there can be many codes for a term in coded_term
- GNUmed looks at coded_term.term = episode.description
whenever it wants codes for the episode name
- new episodes of previously used descriptions automatically
"have" codes *in*directly associated with them
- renaming episodes automatically breaks the previous associated
codes (and automatically associates other codes if known)
- you cannot have different code lists for the same term in different patients
-> you need to be more specific in your naming of episodes
to differentiate
(there will be another table holding code/official_term/system
but this does not have any relevance to the argument
presented here)
#--------------------------------------------------------------------
2) codes are *linked* to certain structures of the EMR but bear no direct equivalence
to particular pieces of text within the EMR
create table code (
pk serial
code text
official_term text
system text
unique(official_term, code, text)
)
create table episode (
pk serial
description
)
create table lnk_code2episode (
fk_code references code(pk)
fk_episode references episode(pk)
unique(fk_code, fk_episode)
)
Note how now
- each episode IS directly linked to specific codes
- code DOES have unique(official_term, code, system)
With this setup
- there can be many codes for a term in code - one per system
- there can be many codes linked to one episode - but each only once
- GNUmed looks at lnk_code2episode to find the codes linked to this episode
- new episodes of previously used descriptions do not *automatically* have any codes
- renaming episodes carries over the previously linked codes, regardless
- good for typos
- bad for semantic changes
- you can have different code lists for the same episode in different patients
- you can name *all* episodes alike and still have different codes per patient
- you can name *all* episodes differently and still link the same codes
- this explains that codes do not *stand for* episode.description but
are simply linked to the EMR as additional data just like, say, a
vaccination - except that the reason for linking is made obvious
(namely that the used decided on linking by way of the episode)
#--------------------------------------------------------------------
So, pick your poison :-)
Karsten
--
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E167 67FD A291 2BEA 73BD 4537 78B9 A9F9 E407 1346
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