Adding custom QUANTITY units

Hi all,

We are currently using the Archetype Designer to create a template for recording historical medications.

One of the issues we’ve come up against is adding custom units to the list available in the “Dose” node (Quantity type).

Specifically, we want to be able to add things like “Tablets”, “Puffs”, “Drops”, etc to the list. So when a medication with a specific dose is selected, the clinician can use one of these units to accurately record the dose.
e.g. Medication = Paracetamol 500mg, Dose = 2 tablets, Timing frequency = 4/day

The Archetype Designer only seems to allow us to select units that are in the UCUM or openEHR set. And doesn’t allow us to add any custom units.

Does anyone know how we could solve this issue?

Thanks in advance,

There has been considerable discussion on this in the past, but to be honest I’m a little confused too.

Previously we had CLUSTER.dosage.v1 which had to have a separate data element for units, such as you describe.

Then there was this discussion - Medication amounts and units and CLUSTER.dosage has been updated to v2.

However, I’m not sure how this has landed or if it has been finalised. I can’t see how to represent the units using current tooling either.

@siljelb @ian.mcnicoll @joostholslag - has the previous thread been resolved. If so how?

I’m not aware of the details. @siljelb would best answer this question, but she may be unavailable for some time. So let me know if you want me to try and dive in to help.

Hi @joostholslag - any help you could provide would be very much appreciated!

Hi Kieran,

The openEHR Reference model was updated recently to allow the use of such custom units but I am not clear if it is supported yet in Archetype Designer or in the various CDRs.

The work around in the Medication archetypes was to hold the amount as a ‘qualified real’ (UCUM unit ‘1’) with a separate element to hold the custom unit…

We can try to find out from tech colleagues where we are in terms of wide support for the new arrangement.


Ian’s response pretty much sums up the current situation. I’d only like to add that if you need to do this in the short term and there isn’t tooling support, I’d use the previous published versions of the relevant archetypes. They’ve been set as deprecated, so you’ll need to search specifically for them, see below:

1 Like

Thanks @ian.mcnicoll and @siljelb.
I think for the time being we’ll need to use the previous version of the archetype, until there’s wider support.

Thanks all for the help!

1 Like

This would be good to know.

We may need to consider reverting the v1 if the tooling can’t support the v2