RE: [NMusers] Minimum patients number...

Mark,

Although I realize that the rules of thumb are well-intended ways to help
less experienced along, the data requirements are so situation-dependent
that any such general rule is likely to guide in the wrong direction more
often than not.

If indeed the "empiric observations" you refer to is from a database
collected and analyzed for the purpose of coming up with these rules, it
would be interesting to learn more about it. Otherwise, I guess it is like
most rules of thumb that we try to formulate - just a best guess by an
experienced analyst.

Best regards,
Mats


Mats Karlsson, PhD
Professor of Pharmacometrics
Div. of Pharmacokinetics and Drug Therapy
Dept. of Pharmaceutical Biosciences
Faculty of Pharmacy
Uppsala University
Box 591
SE-751 24 Uppsala
Sweden
phone +46 18 471 4105
fax +46 18 471 4003
mats.karlsson_at_farmbio.uu.se


        
        

        



-----Original Message-----
From: owner-nmusers_at_globomaxnm.com [mailto:owner-nmusers_at_globomaxnm.com] On
Behalf Of Mark Sale - Next Level Solutions
Sent: Saturday, January 27, 2007 20:50
Cc: nmusers_at_globomaxnm.com
Subject: RE: [NMusers] Minimum patients number...

Mats,
  The "rules of thumb" are indeed empiric observations from one
variable. But, if you have two dependent variables, you have twice the
data (one time point, two DVs), and twice the parameters. So, I think
the rule may be consistent, but I don't know how valuable it is in the
first place.



Mark Sale MD
Next Level Solutions, LLC
www.NextLevelSolns.com


> -------- Original Message --------
> Subject: RE: [NMusers] Minimum patients number...
> From: "Mats Karlsson" <mats.karlsson_at_farmbio.uu.se>
> Date: Sat, January 27, 2007 11:41 am
> To: "'Ahmed Hawwa'" <ahawwa1_at_yahoo.com>, <nmusers_at_globomaxnm.com>
>
> Hi,
>
> I think that all the rules of thumb that have been mentioned are based on
> the assumption that you have a single observed variable. If you observe
> several, you certainly can expect to estimate more parameterers.
>
> Mvh,
> Mats
>
>
> Mats Karlsson, PhD
> Professor of Pharmacometrics
> Div. of Pharmacokinetics and Drug Therapy
> Dept. of Pharmaceutical Biosciences
> Faculty of Pharmacy
> Uppsala University
> Box 591
> SE-751 24 Uppsala
> Sweden
> phone +46 18 471 4105
> fax +46 18 471 4003
> mats.karlsson_at_farmbio.uu.se
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: owner-nmusers_at_globomaxnm.com [mailto:owner-nmusers_at_globomaxnm.com]
On
> Behalf Of Ahmed Hawwa
> Sent: Saturday, January 27, 2007 02:10
> 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 Sun Jan 28 2007 - 15:49:45 EST