I am hesitant to enter this discussion, but here goes.
An assessment scale which assigns a numeric score as well as a symbol/term
is not an ordinal scale. The symbols do in fact comprise an ordinal scale
("very low" < "low" etc). However the numerics provide something else -
usually to be added up with other scores. The designers of such scales are
bound to validate the composite numeric scores (cf SF36).
What you then have is ordinal symbol + real number. If the scale designer
needs to use decimals, that is their choice.
It might be worth looking at the measurement theory literature.
Cheers
Mark
Mark S Leaning PhD
From: [email protected]
[mailto:openehr-clinical-bounces at chime.ucl.ac.uk] On Behalf Of Thomas Beale
Sent: 20 April 2010 15:19
To: openehr-clinical at openehr.org
Subject: Re: ??? DV_CODEDQUANTITY
this has clearly happened because the designers of the scale did not have
the term 'very very slight' in the beginning, but unfortunately they had
already chosen contiguous integers. I have to say, this scale looks quite
subjective. I would be amazed to discover that a) the middle terms were
being used in the same way across all users or that b) the outcomes would be
any worse if a 3 or 5 item scale was used instead. But I am not a doctor, so
ignore that comment ;-)
Practically speaking, I guess we are in the realm of having to create an
ordinal kind of concept to deal with scales with retro-fitted non-integer
items. A pragmatic approach might be to add a DV_ORDINAL variant called
something like DV_SCALE_VALUE which is the same model as DV_ORDINAL but with
the value of Real rather than Integer type.
- thomas beale
On 20/04/2010 12:35, Ian McNicoll wrote:
Assessment scales provide a rich seam of frustration for developers, with
their seemingly limitless capacity for arbitrary scales and quantities.
Here is a current example about which I have been asked for advice - the
Borgscale (http://www.ac6v.com/karlaz2.htm).
It is a scale from 0-10, so would be ideal to express as a DV_ORDINAL but
includes 0.5 which makes this impossible.
There are a number of workarounds but is there a case for adding some form
of Coded Quantity datatype to openEHR? The primary problem is in
representing such constraints in archetypes but there might be some value in
simplifying integration from Snomed coded findings.
SCALE
SEVERITY
0
No Breathlessness* At All
0.5
Very Very Slight (Just Noticeable)
1
Very Slight
2
Slight Breathlessness
3
Moderate
4
Some What Severe
5
Severe Breathlessness
6
7
Very Severe Breathlessness
8
9
Very Very Severe (Almost Maximum)
10
Maximum
Ian
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