Simbiology program code gave different results from my custom code

Hello team,

I am working on a population pharmacokinetics (PK) project, so I am using sbiofitmixed() to solve the model.

However, I found that the fit program code directly exported from Simbiology Model Analyzer gave me different results from my custom code. Although I have all the settings set as the same, I have a problem with the parameter estimation on ka_Central.

My Simbiology Model Analyzer code can estimate this parameter with high confidence, but my custom code cannot.

I tried debugging but could not find where the problem came from.

Please find the code in the attachment file.

Thank you very much.

Jesse

Answer 1

[Jeremy Huard]

Hi @Jesse Chao,

the issue comes from the dose template. In the first version your taget is Drug_Central (corresponding to IV bolus) whereas in the second the tdrug target is Dose_Central (corresponding to EV).

Since no absoprtion takes place in the first version, ka cannot be estimated.

If you change the drug target to Dose_Central, you will be able to estimate ka.

Best,

Jérémy

[Jesse Chao]

Hello Jérémy,

What a naive mistake from me. Thank you for your precious time to point it out.

Hope you have a nice day Jesse

Answer 2

[Jeremy Huard]

Hi @Jesse Chao,

this is difficult to debug without the actual model and data.

Would you be able to share them?

That said, I noticed a discrepancy in the initial values of both versions because of the order of estimated parameters (ka, Central, CL) instead of (ka, CL, Central).

Best,

Jérémy