Stream: implementers
Topic: Dosage timing question
Marten Smits (Mar 24 2020 at 13:11):
Hi I'm trying to model the following dosageInstruction: Once every 8 weeks, take 2 times a day 500mg. But it seems I'm missing a "frequencyUnit" element or something. For now I'm getting this:
<dosageInstruction>
<timing>
<repeat>
<frequency value="2"/>
<period value="8"/>
<periodUnit value="wk"/>
</repeat>
</timing>
<doseQuantity>
<value value="500"/>
<unit value="mg"/>
<system value="http://unitofmeasure.org"/>
<code value="mg"/>
</doseQuantity>
</dosageInstruction>
I would like to specify the 2 times a day part, instead of just "2". Is there a way to do that? An option I'm missing in timing?
Lloyd McKenzie (Mar 24 2020 at 13:27):
@Melva Peters
Jean Duteau (Mar 24 2020 at 15:04):
I don't think you can do that because you have two different frequencies - the "once every 8 weeks" part and then the "two times a day" part. I'm assuming that you take it twice on one day and then wait eight weeks? The best that I can come up with is saying to take it twice a day for one day and then have a 2nd dosage instruction with the same timing but 8 weeks later. If this is supposed to be an ongoing thing, then that won't work, so you'll have to fall back to text.
Lloyd McKenzie (Mar 24 2020 at 15:08):
Or an extension
Jean Duteau (Mar 24 2020 at 15:08):
true
Jose Costa Teixeira (Mar 24 2020 at 15:40):
would that be a standard extension?
Like the transition in v2 (I think around v2.3 or so) where we made the TQ1 segment which enabled much bigger variety.
Jean Duteau (Mar 24 2020 at 15:41):
the ability to have a timing within a timing (which is what this needs)? I'm not sure that's quite standard.
Jose Costa Teixeira (Mar 24 2020 at 15:50):
yes, to have timings grouped by timings
Marten Smits (Mar 24 2020 at 15:56):
Jean Duteau said:
I don't think you can do that because you have two different frequencies - the "once every 8 weeks" part and then the "two times a day" part. I'm assuming that you take it twice on one day and then wait eight weeks? The best that I can come up with is saying to take it twice a day for one day and then have a 2nd dosage instruction with the same timing but 8 weeks later. If this is supposed to be an ongoing thing, then that won't work, so you'll have to fall back to text.
Thank you Jean, that is all I needed to hear. Falling back on text was my preference as well in this case. Thank you for confirming this can't be done structurally in standard FHIR for now.
Vadim Peretokin (Feb 28 2022 at 08:37):
I've got the same problem: the frequency needs to be specified twice instead of once and the two frequencies are combined with a logical AND. For example "5 times a day monthly" means once a month, take this 5 times during the day. We need this for DSS so portraying it just as text won't work.
Will be making a modifierExtension for this - thinking on the best format. @Jose Costa Teixeira maybe you have an idea from your v2 work?
Jose Costa Teixeira (Feb 28 2022 at 08:49):
perhaps something including this? https://hl7-definition.caristix.com/v2/HL7v2.6/Tables/0472
Jose Costa Teixeira (Feb 28 2022 at 08:51):
I think FHIR dosage should cover complex dosage instructions but perhaps this is seen as a a European thing so I did not pursue further.
Vadim Peretokin (Feb 28 2022 at 09:11):
I don't see that kind of setup meshing with Timing all too well.
Thinking of adding a frequencyUnit modifier extension, so given the original example -
<timing>
<repeat>
<frequency value="2"/>
<frequencyUnit value="d"/>
<period value="8"/>
<periodUnit value="wk"/>
</repeat>
</timing>
Would mean "twice a day, once in 8 weeks" or "once every 8 weeks, take 2 times".
It's still frequency per period, frequency does not apply evenly over the whole period anymore - just over the frequencyUnit and the two are a logical AND.
Last updated: Apr 12 2022 at 19:14 UTC
