# how to determine that a variable has PQ according to ISO 21090
**URL:** https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876
**Category:** Clinical (archive)
**Created:** [5 February 2009 14:07 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876 "2009-02-05T14:07:55Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@williamtfgoossen](https://discourse.openehr.org/u/williamtfgoossen)
#### Post date: [5 February 2009 14:07 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876/1 "2009-02-05T14:07:55Z")
Dear all,
We are currently working on several archetypes and encounter difficulties in finding the right approach in the Ocean archetype editor.
For instance, a pain scale (VAS type, or numeric 0 -10). According to ISO datatypes 21090 this is a Physical Quantity.
How can this be determined in the editor? We get the option Q to set that it is a quantity. Then there is a wealth of specific units, but not a simple way of stating this is a PQ.
Am I missing the point here?
Sincerely yours,
dr. William TF Goossen
director
Results 4 Care b.v.
De Stinse 15
3823 VM Amersfoort
the Netherlands
email: [Results4Care@cs.com](mailto:Results4Care@cs.com)
phone + 31654614458
fax +3133 2570169
www.results4care.nl
Dutch Chamber of Commerce number: 32133713
---
### Author:  [@ian.mcnicoll](https://discourse.openehr.org/u/ian.mcnicoll)
#### Post date: [5 February 2009 15:11 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876/2 "2009-02-05T15:11:31Z")
Hi William,
Have a look in CKM at
CLUSTER.Symptom-pain [Pain symptom]
Under Current Intensity ,a numeric 0-10 pain scale, is modelled as a
Count, since Pain scale has no agreed international physical units.
Count and Quantity are both sub-classes of Amount in the openEHR ref
model but for Quantity, the units attribute is mandatory (UCUM units).
I see mention of a 'standard 10cm. VAS' . In this case, it could be
modelled as a Quantity, property type Length Units cm. This element
could be included in the archetype alongside the Count element, but I
am not sure that the physical length has any particular significance
and this may just be over-complicating the model. e.g Would a
'large-print' 20cm scale with 10\*2cm intervals not be equivalent?
This was an interesting find via Google -summary of pain scales
[http://www.clinicalinfometrics.northwestern.edu/archive/Tab%208%20Pain%20Measures.pdf](http://www.clinicalinfometrics.northwestern.edu/archive/Tab%208%20Pain%20Measures.pdf)
Regards,
Ian
PS Derek Hoy tells me you will be over in Scotland in the near future.
It would be nice to meet up and say hello.
---
### Author:  [@system](https://discourse.openehr.org/u/system)
#### Post date: [8 February 2009 03:37 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876/3 "2009-02-08T03:37:03Z")
Hi William
I guess the point here is model what clinicians want and understand. I do not think that pain scales have any idea of ‘cms’ – so units does not seem appropriate.
If you want a real with no units, you can use ‘qualified real’ property which allows a blank unit.
Cheers, Sam
---
### Author:  [@williamtfgoossen](https://discourse.openehr.org/u/williamtfgoossen)
#### Post date: [8 February 2009 07:44 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876/4 "2009-02-08T07:44:02Z")
In a message dated 8-2-2009 4:47:16 W. Europe Standard Time, [sam.heard@oceaninformatics.com](mailto:sam.heard@oceaninformatics.com) writes:
> Hi William
>
> I guess the point here is model what clinicians want and understand. I do not think that pain scales have any idea of ‘cms’ – so units does not seem appropriate.
>
> If you want a real with no units, you can use ‘qualified real’ property which allows a blank unit.
>
> Cheers, Sam
Thank you Sam,
This is helpful. One addition to this: is the definition of real also allowing a score on the VAS of say 4.5? So decimals? Some pain scales use the numeric values 0 - 1 - 2 till 10 (the numeric score variant), but others allow setting a cross on a 10 cm line and then the actual score is determined allowing decimals.
Sincerely yours,
dr. William TF Goossen
director
Results 4 Care b.v.
De Stinse 15
3823 VM Amersfoort
the Netherlands
email: [Results4Care@cs.com](mailto:Results4Care@cs.com)
phone + 31654614458
fax +3133 2570169
www.results4care.nl
Dutch Chamber of Commerce number: 32133713
---
### Author:  [@williamtfgoossen](https://discourse.openehr.org/u/williamtfgoossen)
#### Post date: [13 March 2009 10:15 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876/5 "2009-03-13T10:15:15Z")
Hi Sam,
We have tried, but it is not possible to represent a proper VAS scale in the archetype editor.
What clinicians want is exactly as I said before: being able to score a 5, 7, 10 for pain.
This looks like the above instrument in this picture.
But as you can see in some instance the patient will say, my pain today is like a 7.3 or a 3.6 or a 9.9
The qualified Real does not deal with it. So it appears not possible to handle the ISO 21090 PQ datatype which would allow to have a decimal.
Further the qualified real does not allow to set the minimum 0 and maximum 10 score.
If we apply the valid and reliable McGrath for pediatrics, we see the five level faces, where 5 is obvious the ☹ sign (much pain) and the 1 is 🙂 (no pain)
This would really be an ordinal, but stored with a number. For this one the qualified real would do.
So we do experience difficulties in using the archetype editor to proper represent clinical and scientific knowledge.
Hope you can find a solution for this.
Thanks William
In a message dated 8-2-2009 4:47:16 W. Europe Standard Time, [sam.heard@oceaninformatics.com](mailto:sam.heard@oceaninformatics.com) writes:
> Hi William
>
> I guess the point here is model what clinicians want and understand. I do not think that pain scales have any idea of ‘cms’ – so units does not seem appropriate.
>
> If you want a real with no units, you can use ‘qualified real’ property which allows a blank unit.
>
> Cheers, Sam
>
> **From:** [openehr-clinical-bounces@openehr.org](mailto:openehr-clinical-bounces@openehr.org) [[mailto:openehr-clinical-bounces@openehr.org](mailto:openehr-clinical-bounces@openehr.org)] **On Behalf Of** [Williamtfgoossen@cs.com](mailto:Williamtfgoossen@cs.com)
> **Sent:** Thursday, 5 February 2009 11:38 PM
> **To:** [openehr-clinical@openehr.org](mailto:openehr-clinical@openehr.org)
> **Subject:** how to determine that a variable has PQ according to ISO 21090
>
> Dear all,
>
> We are currently working on several archetypes and encounter difficulties in finding the right approach in the Ocean archetype editor.
>
> For instance, a pain scale (VAS type, or numeric 0 -10). According to ISO datatypes 21090 this is a Physical Quantity.
>
> How can this be determined in the editor? We get the option Q to set that it is a quantity. Then there is a wealth of specific units, but not a simple way of stating this is a PQ.
>
> Am I missing the point here?
>
> Sincerely yours,
>
> dr. William TF Goossen
> director
> Results 4 Care b.v.
> De Stinse 15
> 3823 VM Amersfoort
> the Netherlands
> email: [Results4Care@cs.com](mailto:Results4Care@cs.com)
> phone + 31654614458
> fax +3133 2570169
> www.results4care.nl
> Dutch Chamber of Commerce number: 32133713
Sincerely yours,
dr. William TF Goossen
director
Results 4 Care b.v.
De Stinse 15
3823 VM Amersfoort
the Netherlands
emails:
[Results4Care@cs.com](mailto:Results4Care@cs.com)
[williamtfgoossen@cs.com](mailto:williamtfgoossen@cs.com)
info@results4care.nl
phone + 31654614458
fax +3133 2570169
www.results4care.nl
Dutch Chamber of Commerce number: 32133713
---
### Author:  [@system](https://discourse.openehr.org/u/system)
#### Post date: [16 March 2009 06:33 UTC](https://discourse.openehr.org/t/how-to-determine-that-a-variable-has-pq-according-to-iso-21090/14876/6 "2009-03-16T06:33:54Z")
Hi William
I am not sure of the requirements but I think you want a real number between 0 and 10.
You are right that there is a bug in Qualified Real that does not allow you to set a max and min value (this has been added to Jira).
The most correct way to deal with this is as a proportion (on the grounds that a real number on its own in medicine is a ratio or proportion of some kind). This needs to be unitary (ie denominator of 1). The ADL looks like:
ELEMENT[at0005] occurrences matches {0..1} matches { – Pain
value matches {
DV\_PROPORTION matches {
numerator matches {|0.0..10.0|}
type matches {1}
}
}
}
Hope this is helpful and thanks for finding the problem with the qualified real.
Cheers, Sam
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