RE: [NMusers] Minimum patients number...

You can simulate many data sets (let say 100)for all the potential
designs you have in mind (assuming prior knowledge of the population
parameters).
For each design,you fit the model to these 100 data sets.
The standard deviation of all the population estimates across the 100
different data sets gives you a hint about the standard error you should
expect for a new non simulated data set. This standard error divided by
the mean *100 gives you some information about the expected precision
associated with the population parameters. My experience taught me that
expecting between 5-15% for the mean, 20-50% for the variances is good
(some covariance can lead to really high % imprecision).
If you perform the same strategy for other designs, you can then make
your mind about the one that match your criteria.
Serge Guzy
President POP-PHARM

-----Original Message-----
From: owner-nmusers_at_globomaxnm.com [mailto:owner-nmusers_at_globomaxnm.com]
On Behalf Of Ahmed Hawwa
Sent: Friday, January 26, 2007 5:10 PM
To: nmusers_at_globomaxnm.com
Subject: RE: [NMusers] Minimum patients number...

Hi all,

Thank you all indeed for the valuable commenets. I have actually 19
patients only and I need to look into the PK parameters of two
metabolites.

Minimum 10 patients per eta would mean 50-60 patients.
I'm sure this number would give optimal results but as a matter of fact
I don't think I would be able to reach it.

> I would suggest that you assess each case on its merits and determine
> the effectiveness of any proposed design using either simulation
> linked with estimation (which is tedious, slow, not optimal but often
> effective)

Regarding using simultation do you mean to put certain values of thetas
and then run a simulation and compare results with the actual
concentrations or did I miss the point?

> or an
> information theoretic technique (such as optimal design).
> The optimal design software WinPOPT
> (www.winpopt.com), which is freely
> available, allows you to rapidly assess the effectiveness of various
> designs as well as optimize a design within your specific study
> constraints (e.g.
> clinic visit times etc).

I think one of my study constrains is clinic visit times since patients
taking our drug are actually outpatients and we are able to collect one
sample only at each clinic visit. would this software be of any help??

Looking to hear from you soon.

Regards,
ahawwa



 
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Received on Fri Jan 26 2007 - 21:54:09 EST