Hi Peter,
I assume from the question that the baseline is the baseline of your
modeled PD measure, not of some other value (like the baseline weight),
and that you model the actual PD measure, not change from the baseline.
Then
- it would be more logical to use the model-predicted baseline;
- for the clinical applications it could be more useful to have observed
predictor;
- for simulations of future studies it could be more convenient to have
everything in the model rather than use observed values (especially if
you apply the model to different population where the baseline value
could be shifted).
I would try both versions to see the differences, and then use the one
that is more convenient to use in the particular situation.
Best regards,
Leonid
--------------------------------------
Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
web: www.quantpharm.com
e-mail: LGibiansky at quantpharm.com
tel: (301) 767 5566
On 8/11/2010 11:21 AM, Peter Bonate wrote:
I'd like to get the group's opinion on something. I have a pharmacodynamic
model and the baseline was shown to be a covariate on one of the model
parameters. I was hoping to get general thoughts on the use of the baseline as
a covariate. Is there a preference for using the observed baseline vs. NONMEM
predicted baseline? And does your opinion change if you have a large residual
error?
Thanks
Pete bonate
Peter L. Bonate, PhD, FCP, FAAPS
GlaxoSmithKline
Clinical Pharmacology, Modeling, and Simulation
5 Moore Drive, 17.2259
Research Triangle Park, NC 27709
phone: 919-483-7534
fax: 919-483-8948
email: [email protected]
