Hi everyone! Do we have a way to represent a change over time as a proportion rather than as an absolute measurement? For example: Weight change from one measurement to the next, we can express that in a number of kg using the OBSERVATION.body_weight and an interval event with the math function “…

Where would the ‘10 Kg’ part be stored in the data? Is that another element in the weight archetype? Is in the interval itself?

The ‘10 kg’ would be stored in the main “Weight” DV_QUANTITY element, modified to mean “change” and not “actual” by the math function of the event.

Oh, I see it now. The only thing I can thing about is that Percent (%) is a valid UCUM unit , and as such could be used in the quantity just fine by itself. Adding that as a valid unit in the archetype (I’m assuming an additional “0.0…100.0 %” constraint) would work. If you want to put both at the s…

At the moment you can: define the two change fields, and use application level calculation to populate the derived field value, i.e. the %. define just the raw delta field, and compute the % change purely in the application layer - since it is derived by a simple calculation, this is always doable…

I’m not sure I understand, but here goes [image] thomas.beale: define the two change fields, and use application level calculation to populate the derived field value, i.e. the %. So basically two instances of the relevant OBSERVATION (say, Body weight) each with a POINT_EVENT, and always ca…

[image] siljelb: So basically two instances of the relevant OBSERVATION (say, Body weight) each with a POINT_EVENT, and always calculate the % change on the fly? You can actually mix Event types within a single History structure. So you can have differential and absolute value events within t…

I’m not so sure that this example is a good clinical requirement on which to propose possible RM changes. Recording an actual body weight at a point in time is one clinical concept. Recording a change in body weight over an interval, as an actual in ‘kg’ or as ‘%’ is a semantically separate co…

[image] heather.leslie: In fact I’m of the opinion that actual weight and the change in weight should be recorded as two discrete clinical concepts in two separate archetypes. I would not go that far - it’s still body weight we’re talking about. You could archetype two alternative History str…

Modelling for clinical and implementation clarity is really important. If we model something very elegantly but we can’t easily explain it for review or implementation then we have a problem. If we have both the weight as ‘actual’ and weight as ‘change’ that is theoretically ok. But when we can only…

[image] heather.leslie: Modelling for clinical and implementation clarity is really important. If we model something very elegantly but we can’t easily explain it for review or implementation then we have a problem Can’t really argue with that. Slight philosophical note: there is a question (…

Change over time in an OBSERVATION measurement, represented as %

Clinical

siljelb (Silje Ljosland Bakke) 10 February 2022 14:34 15

We had a discussion about Z-scores a while ago: Z-scores and percentiles

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Change over time in an OBSERVATION measurement, represented as %

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