Allometric scaling for pediatric patients prediction

[jzhou2009]

Hi there, I'm not sure if anyone has experience using the model to predict pediatric patients? So we have a project where we would like to use the model to predict the calcium concentration in pediatric patients after calcium intake in particular.

• There is no weight component in the code and the code seems to assume a subject with 70 kg weight (e.g. the extracellular fluid was assumed to be 14 L for calcium). has anyone had allometric scaling experience with the model?
• And I'm also writing to see if anyone has ideas about whether age/weight would affect the calcium mass transfer from bone to plasma, calcitriol, Vitamin D, PTH, or calcium/phosphorus intake?

I really appreciate if you can offer some ideas to predict pediatric population using the current model. Thank you! Regards, Jie

[riggsmm]

Hi Jie, Sounds like a really interesting possible application. To date, we've been able to apply the model to a range of adults populations and in different disease state, though have not scaled the model into pediatrics. I'd be curious to hear more about how this goes as you proceed.

A few thoughts on things to look out for:

1. As you mention the "volume" for the various electrolytes is set at 14 L. This was a carry over from one of the models (the Raposo et al model) that feed into integrated calcium bone model. Scaling for that volume based on body weight would seem a reasonable first approach.

2. Consider organ-level (maturational) differences: e.g., renal filtration, bone deposition is typically much different in children (as a net influx as bones are growing) compared to adults (e.g., net loss in older adults), and I'm not sure about dietary differences or not (impact of vitamin D / bioavailability of calcium, etc.).

3. It may be fair to start by assuming that some of the effects are constant (same) between adults and children, e.g., I would think that calcium sensing and PTH response would be consistent (in healthy states across age groups) given the exactness by which serum Ca concentrations are maintained. Though even this assumption is worth testing / investigating.

I do recall seeing reports on longitudinal calcium balance and bone growth in pediatrics; though it wasn't a focus of mine because of the populations we were investigating, I'm hopeful that you can find the level of information needed to check many of these questions.

Hope it goes well and please do post questions and progress here! Looking forward to updates.

Thanks, Matt

[jzhou2009]

Hi Matt, Thank you for your reply! Now we proposed to do a series of sensitivity analysis on the parameters as you listed and other literature findings on the model. I will update if the model can be workable for pediatrics.

Thanks again for your help! Regards, Jie