> classifications are conceptually non-overlapping coding schemes for
> analysis of population based data.

One purpose of classifying terms is certainly to help analyse population
data. This is not the only reason you might want to classify, however.
In the context of decision support, for example, you need classification
to tell you that:

	IF there is a rule which say that patients with 'Unstable Angina'
	should have an immediate ECG

	AND your patient is documented as having 'severe unstable angina'

	THEN 'severe unstable angina' is a kind of 'Unstable Angina', and
	your patient needs an immediate ECG.

Another reason why you need to classify terms is in order to provide
some means of guiding users to the correct term.

> Nomenclatures/Thesuarsus are for recording and retrieving data at a patient level.

I have grave doubts about these definitions of 'classifications' and 'nomenclatures'.

A nomenclature is any system of naming or labelling of things.
A thesaurus, typically, is a systematic cross-referencing of terms in
different nomenclatures based on their semantic similarity.
A classification is a system by which elements of a nomenclature are
organised by class or type.

It is, therefore, impossible to have a classification unless you are
also a nomenclature (you have to have something to classify).  It is
possible to be a nomenclature without having any classification, in
which case you are a dictionary.  A nomenclature which has been
classified is still a nomenclature.

Therefore, ICD, SNOMED and READ are all nomenclatures.  They are also
all classified to one degree or another.  It is a spurious and
confusing distinction to say that something is 'A Classification' if it
does not have much detail, but 'A Nomenclature' if it does.  In
discussing any suggested term-set for use in medicine, we must
separately identify whether both the scope AND the classification of
that nomenclature is correct and adequate for our purposes.  Saying
'never mind the quality, feel the width' isn't very helpful.

> Read is one of only two nomenclatures in the world; the other being Snomed.

Clearly wrong (see above). There are more than 300 different nomenclatures
in the field of medicine alone.

> Classifications should be mapped to Nomenclatures.

What does this mean? Consider a nomenclature like ICD, which has an associated
classification, and another nomenclature such as the Oxford Dictionary of Medicine
(which does not). How would you map them?

On the other hand, if what you really mean is:

Not very detailed, classified nomenclatures should be mapped to other
not very detailed, classified nomenclature and also to more detailed,
classified nomenclatures.

...then I agree with you. It's quite a feat to actually DO it, though,
especially in the context of mapping not very detailed, classified
enumerative nomenclatures (such as ICD) to very much more detailed,
classified and compositional nomenclatures (like READ 3 or GALEN).

> Read is to code things at a detail required by the clinician.
> It does not classify as there is often conceptual overlap. You need mapped
> classification for this purpose.

In what way does it 'not classify' ? It has a hierarchical arrangement of
codes, according to class, does it not ? It uses this hierarchy explicitly
to inherit rules of constraint. What it doesn't do is classify things according
to how an epidemiologist might expect them to be classified. In other words,
the particular choice of classes used is for a different purpose than,
for example, ICD.

> All the crap in the press is irrelvant to the fact we need a working
> version of Read 3.1. We haven't got one yet.

What criteria would you put forward to determine whether you *had* got
a working version of READ 3.1 ? How would you test whether those criteria
had been met ?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr Jeremy Rogers MRCGP DRCOG DFFP MBChB
Clinical Research Fellow
Medical Informatics Group
Department of Computer Science
Manchester University, Oxford Road
Manchester, United Kingdom
M13 9PL

(+44) 161 275 6145 voice
(+44) 161 275 6932 fax
[log in to unmask]
URL http://www.cs.man.ac.uk/mig/people/jeremy.html
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~





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