RE: [NMusers] Minimum patients number...

Ahawwa

> 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.

This would be empirical - not optimal.

> 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?

Yes. With a specified model, THETAs, OMEGA elements and SIGMA elements
simulate several hunderd data sets under a given design and then estimate
the parameters for each of the simulated data sets. The standard deviation
of each parameter from the estimation runs is approximately equivalent to an
asymptotic standard error. Then change your design somehow and repeat the
process...

The problem with the simulation-estimation approach is that it is cumbersome
to include uncertainty in your parameter and model space. Whereas in
WinPOPT (and similar programs) it is simple to include a number of candidate
models and parameters sets for each model and then evaluate the best design
averaging over all candidates. Thereby producing a design that is robust to
your starting conditions. {Afterall if you knew the model and parameter
values exactly then you wouldn't need to do the proposed PK study - so
quantifying your uncertainty is important.}

> > 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??

Yes. I use it for this purpose regularly. You can explicitly set up
constraints on samples in relation to clinic visits. There are currently
more than 30 groups who use WinPOPT worldwide for this purpose.

It is important to consider that, as with all new concepts, there will be a
learning curve, both in using WinPOPT and also (and importantly) in
conceptualising how to put your design together irrespective of the choice
of software.

Regards

Steve
--
Professor Stephen Duffull
Chair of Clinical Pharmacy
School of Pharmacy
University of Otago
PO Box 913 Dunedin
New Zealand
E: stephen.duffull_at_otago.ac.nz
P: +64 3 479 5044
F: +64 3 479 7034

Design software: www.winpopt.com
 

Received on Fri Jan 26 2007 - 21:35:54 EST