sbiofit example - Fit a One-Compartment Model to an Individual's PK Profile using SimBiology app

Hi,

I am trying to replicate the example "Fit a One-Compartment Model to an Individual's PK Profile" from the sbiofit help page (https://se.mathworks.com/help/simbio/ref/sbiofit.html) but using the SimBiology GUI instead of doing it programmatically; see attached files.

Unfortunately I cannot replicate the results as the fit variables, volume of the central compartment and clearance, are different compared to the values found programmatically (in particular, they are equal to the set initial value). Does anyone know what I am missing?

Also, I have the following additional questions:

• Why is ka_Central not estimated in this case? Shouldn't it be estimated as it is part of the one-compartment model used here?

• What happens if a dose has different units? E.g. gram instead of milligram for this particular example? Does SimBiology automatically detect the different units and convert them appropriately?

Hope my explanation is clear enough,

Many thanks,

Jacopo

Answer 1

[Jeremy Huard]

Hi Jacopo,

I have had a look at your project. There were two things which differed from the programmatic example:

• you set the response to be a measurement of Dose_Central whereas it should have been Drug_Central
• unit conversion was not turned on. That being said, it would not prevent you from getting the right results because the model and dataset are in the same units.

I have attached your project with these modifications.

Let me now answer your questions:

• Why is ka_Central not estimated in this case? Shouldn't it be estimated as it is part of the one-compartment model used here?

ka_Central is not estimated because we only have IV data in this example. The dose is given to Drug_Central and we measure Drug_Central. So, we wouldn't have any information in this dataset to estimate ka_Central.

• What happens if a dose has different units? E.g. gram instead of milligram for this particular example? Does SimBiology automatically detect the different units and convert them appropriately?

SimBiology can deal with different units as long as they are all using amounts or all using mass. For this, you need to activate unit conversion by clicking on this button in the Model Tab of the SimBiology App:

Best regards,

Jérémy