Andreas,
I think if you have only study-level data, you can treat each study as a
"subject", build meta-population dose-PD model in the usual way,
IPRED=Emax (or some other) function of DOSE
and modify the error part as follows: For each data point, you know the
mean value (DV), SD, and N. From SD and N you can get an estimate of
standard error of the mean as SE=SD/sqrt(N) (computed for each data
point and included into the data file). Then your error model would include
Y=IPRED+SE*EPS(1)
I am not sure whether you need to fix SIGMA
$SIGMA
1 FIXED ; for EPS(1)
thus assuming that all error in your model comes from the "assay", or
estimate it thus allowing for unexplained model misspecification and
extra error. I would try both ways to see the difference.
This is the simplest version that can be further improved (? or at
least, made more complicated) by adding the study effect on error (thus
accounting for possible differences in study populations;
Y=IPRED+SE*EXP(ETA(1))*EPS(1)), etc.
Leonid
--------------------------------------
Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
web: www.quantpharm.com
e-mail: LGibiansky at quantpharm.com
tel: (301) 767 5566
[email protected] wrote:
Dear NMUSERS,
I wanted to investigate the dose-response relationship (Emax model) of a
drug with NONMEM, based on data from literature (i.e. a meta-analysis).
However, I am not quite sure how to deal with the different levels of
random effects. Suppose I have 10 studies of different size where
different doses were given and the response is presented as average
change of a biomarker +/- standard deviation for each dose level. How
would I incorporate the standard deviation of the biomarker measurements
reported in each study for each dose level and how would I account for
the different number of patients in the study?
I would greatly appreciate your help, maybe with a NM-code snippet or
reference to a paper where something similar has been done.
Thanks in advance, Andreas.
Ferrer
Andreas Lindauer
Pharmacokineticist
Pharmacokinetics and Metabolism
R&D Center. Ferrer Internacional S.A.
Juan de Sada 32, 08028 Barcelona
[email protected]
www.ferrergrupo.com
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