NONMEM Users Network Archive

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RE: simulation question

From: Ribbing, Jakob <Jakob.Ribbing>
Date: Fri, 6 Feb 2009 11:00:26 -0000

Ethan,

 

Sebastian is right that a non-parametric bootstrap may be suitable for
determining the uncertainty in the population parameters. However, I got
the impression that you wanted to investigate possible study designs on
how informative they are for a future model-based analysis? If you would
like to do simulation based on your current best guess of the model
parameters (i.e. the point estimates) and you would like to do model
based analysis of the future study in isolation, then PsN has another
program which is highly efficient and would automatically provide you
with summary statistics, without any programming required. This program
is called sse for stochastic simulation and estimation:

http://psn.sourceforge.net/PDF_docs/sse_userguide.pdf

 

sse would also allow you to investigate the performance of alternative
models, e.g. simulation with a two-compartment model and estimation with
a one-compartment model, to see if CL can be estimated with good
precision and low bias, even from the sparse data of a future study.

 

You need to generate the data sets with the study designs yourself, but
the rest is really slick. If you are planning to analyse the new study
in conjunction with the currently-available data (i.e. a pooled
analysis) there may be some clever way of tweaking sse into evaluating
this, but I could not say exactly how to best achieve that. (maybe
someone in Uppsala has a suggestion in that case)

 

Best regards

 

Jakob

________________________________

From: owner-nmusers
On Behalf Of Sebastian Ueckert
Sent: 06 February 2009 09:51
To: Ethan Wu
Cc: nmusers
Subject: Re: [NMusers] simulation question

 

Dear Ethan,
the simplest solution to solve your problem would be to use the
bootstrap command of PSN (http://psn.sourceforge.net/). With PSN
installed you would simply do:

bootstrap final_model.mod -samples=200

PSN would take care of unsuccessful runs and provide a nice summary of
the individual estimates.

Best regards
Sebastian

On Thu, Feb 5, 2009 at 11:18 PM, Ethan Wu <ethan.wu75

Dear users,

  I am trying to compare several specific PK/PD study designs by:

 -- run 200 simulations with the final model (develope from original
dataset)

 -- fit the final model to the 200 simulated dataset

To achieve above, I used $SIM SUBPROB=200 option

 however, nonmem would completely stop after running into estimation
problem at one specific simulation/estimation cycles, for some designs
it stop even before 10th iterations.

Is there anyway nonmem could continue go on?

Or, does someone know alternative way to achieve the goal?

thanks

 

 

 


Received on Fri Feb 06 2009 - 06:00:26 EST

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