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Re: PRIOR method without covariance matrix of estimates?

From: Norman Z <freecg>
Date: Fri, 14 Oct 2011 22:45:34 -0400

Hi Leonid,

Would you please explain why combine the data may be a better option than
using priors? I've met similar situations.

Thanks,

Norman

On Fri, Oct 14, 2011 at 5:01 PM, Leonid Gibiansky <LGibiansky
m
> wrote:

> Nele,
>
> Nonmem 7.2 has UNCONDITIONAL option in cov step that would compute SEs ev=
en
> for problems with error in minimization.
>
> Also, it is perfectly OK to have variance-covariance computed from
> bootstrap; some may even argue that it is better than use Nonmem cov matr=
ix.
>
> And finally (just an opinion) I would rather combine the data than use
> priors.
>
> Thanks
> Leonid
>
>
> ------------------------------**--------
> Leonid Gibiansky, Ph.D.
> President, QuantPharm LLC
> web: www.quantpharm.com
> e-mail: LGibiansky at quantpharm.com
> tel: (301) 767 5566
>
>
>
>
> On 10/13/2011 1:31 AM, Kaessner, Nele wrote:
>
>> Dear all,
>>
>> I am currently in a planning phase for a PopPK evaluation for an
>> upcoming study. I have already developed a PopPK model for this
>> compound, and the idea would now be to fit the available model to the
>> new data. One idea was to do this via the PRIOR functionality in NONMEM,
>> so that I do not have to mix the old data into the new data set. So now
>> I wanted to test the performance of this approach via simulations, and
>> have the following problem:
>>
>> My previously developed final model did not converge successfully
>> (terminated with rounding errors), so I do not have a covariance matrix
>> of estimates to describe the uncertainty in the THETAs. However I
>> obtained confidence intervals from a nonparametric bootstrap, and I was
>> wondering if these results can somehow be used instead for the prior
>> information.
>>
>> In some internal discussions we had the idea to just use all the
>> parameter estimates from the performed 1000 bootstrap runs, and just
>> calculate variance and covariance of THETAs from these.
>>
>> I would highly appreciate your comments on the validity of such an
>> approach, or suggestions of other alternatives.
>>
>> Thanks and best regards
>>
>> Nele
>>
>> ______________________________**______________________________**__
>>
>> Dr. Nele Kner
>>
>>
>> PK/PD Sciences
>>
>> Modelling and Simulation (RDP/MS)
>>
>> *Nycomed: A Takeda Company*
>>
>>
>> Nycomed GmbH
>>
>> Byk-Gulden-Str. 2
>>
>> D-78467 Konstanz, Germany
>>
>> Fon: (+49) 7531 / 84 - 4759
>>
>> Fax: (+49) 7531 / 84 - 94759
>>
>> mailto: nele.kaessner
le.kaessner
>> >
>>
>> http://www.nycomed.com <http://www.nycomed.com/>
>>
>>
>> County Court: Freiburg, Commercial Register HRB 701257
>>
>> Chairman Supervisory Board: Charles Depasse (Speaker)
>>
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Received on Fri Oct 14 2011 - 22:45:34 EDT

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