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high shrinkage solutions

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#1 amashehri



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Posted 22 October 2021 - 11:30 PM

Hi, I am trying to build a model to fit a plasma conc for a drug after a single dose. I created a base model with two compartments and Tlag. I got a reasonable fit, but I still get very high shrinkage in one of the Pk parameters (Vd)
Would you please take a look to see if there is any way to decrease the shrinkage value?
I have attached the model below.

Attached Files

#2 Simon Davis

Simon Davis

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Posted 23 October 2021 - 07:03 AM

Hi Amashehri, 

   I'm not sure if there is anything you can to decrease the shrinkage; it is a diagnostic that tells you the data does not have enough information to estimate random effects on this parameter.  I think with the second compartment parameters identifiability can be an issue, since even when you remove random effects for  v2, shrinkage is still a little high for CL2 


    I don't think considering covariates would help, but I'd be interested to hear others experiences.

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  • cl2.jpg
  • ran_eff.jpg

#3 amashehri



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Posted 05 November 2021 - 02:49 PM

Thanks Simon for your reply 



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