[NMusers] Minimum patients number and reference to Laputa in Gullivers Travels

Mats,
 These "rules of thumb" are exactly as you suspect, a well intentioned
best guess. But, lacking other answers, (and for all this discussion,
I don't recall another answer to the question, with the exception of
Serge, who suggests a simulation based method). It isn't clear to me
that an answer based in experience, admitted incomplete, is more likely
to lead in the wrong direction than no answer at all. I have found the
academic discussion from people smarter than I am very interesting,
just haven't seen an answer to the question (again, except perhaps from
Serge who I agree with, that simulation is the best way to answer the
question or how many. Optimal design is probably a very good, and as
Steve points out a very fast, way to answer when).
  Experience also suggests that practical matters drive sample size as
much as theoretical
> > 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.

At which point, we need the academics to try to rescue an underpowered
study.




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: Sun, January 28, 2007 3:49 pm
> To: "'Mark Sale - Next Level Solutions'" <mark_at_nextlevelsolns.com>
> Cc: <nmusers_at_globomaxnm.com>
>
> 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 - 16:26:37 EST