# Error when Entering Weight -8 SD

**Category:** [Growth Charts](https://forum.rcpch.tech/c/rcpch-digital-growth-charts/6)
**Created:** 2025-08-14 15:57 UTC
**Views:** 11
**Replies:** 2
**URL:** https://forum.rcpch.tech/t/error-when-entering-weight-8-sd/565

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## Post #1 by @Malach1te

Hi All, Apologies if this has been covered before…

Experiencing an issue when plotting against a 17 year old who weighs 16.6kg (Confirmed several times this is correct.)

Get the pop up below which I was expecting to just validate the observation and still plot, but the entries are not plotting on the GC

![image|355x169](upload://Aruhiw4e0CKZWeZByIuxBOJHQIL.png)

I Understand there are no set values for what is allowed, and this is a calculation performed on the API and if the inputs (e.g. weight, age, gestation period, etc.) result in a product +/-8sd, they send a message asking the user to double check if the value they entered is correct. This was justified as (to paraphrase) "to validate against extreme values in case they were entered in error, but still allow them to be entered"

Would like to clarify if this is an issue or intended functionality - Aware that the Latest version is 7.4.1 and we are currently using 7.0.13.

Thanks!

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## Post #2 by @eatyourpeas

Thanks @Malach1te for posting

We have this year finalized validation after lots of discussion to be based on SDS thresholds (rather than absolute ones which had previously been the case). After review of different datasets (see [here](https://forum.rcpch.tech/t/validation-limits-upper-and-lower-limits-for-gestation-bone-health-and-parental-height/527/2) and onward links) for the discussion and rationale we settled on absolute cut-offs for SDS <-8 and >+8 SDS as our definition of impossible. 

There error is therefore behaving as expected.

If you are able to update to 7.4.1 we would definitely recommend that, but it should hopefully not affect the warnings / error messages from the API.

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## Post #3 by @pacharanero

I am not sure how in real clinical practice an otherwise normal 17-year old can possibly weigh 16.6kg?

I understand you have checked the weight @Malach1te - but does the patient have some other medical condition such as achondroplasia that would mean they probably shouldn't be platted against the UK-WHO charts? Is the case being written up for publication in journals?

We have in the past used previous world records to 'calibrate' or sense-check our validation limits, and looking at [this page](https://www.guinnessworldrecords.com/news/2021/8/a-history-of-the-worlds-shortest-people-and-the-countries-theyre-from-668323) there are indeed individuals weighing just 5kg or so - however they all have significant medical conditions like osteogenesis imperfecta or achondroplasia meaning that it is clinically unhelpful to plot them on a UK-WHO chart.

We would happily discuss alternatives to returning a 422 error perhaps (so we don't break the implementation) - or we could talk with the affected clinicians to see what they would find most helpful in the API.

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**Canonical:** https://forum.rcpch.tech/t/error-when-entering-weight-8-sd/565
**Original content:** https://forum.rcpch.tech/t/error-when-entering-weight-8-sd/565