NONMEM Users Network Archive

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RE: adding error term to covariate

From: Ribbing, Jakob <Jakob.Ribbing>
Date: Tue, 29 Jul 2008 21:52:08 +0100

Dear Li,

You are right in thinking that your baseline better not be treated as an
ordinary covariate (where we pretend that the covariate values are
measured without error). Unless you want to be very restrictive in how
to use the model (e.g. change from baseline in a study with similar
design and patients with same baseline distribution), it is best to
estimate the baseline. This also allows you to investigate relations (on
the individual level) between baseline and drug effect/disease
progression, etc.

I am sure you will find many old threads on this topic if you search the
nmusers archive. Additionally, here is a recent article:

Related Articles, LinksDansirikul C, Silber HE, Karlsson MO.Approaches
to handling pharmacodynamic baseline responses.J Pharmacokinet
Pharmacodyn. 2008 Jun;35(3):269-83. Epub 2008 Apr 30.



-----Original Message-----
From: owner-nmusers
On Behalf Of LI,HONG
Sent: 29 July 2008 16:06
To: nmusers
Subject: [NMusers] adding error term to covariate

Dear group,

I have a baseline as covariate in the model, and it is the same
measurement as the modeled variable. To me, it is reasonable to
believe that there is measurement error for this covariate. Is
there a way to incorporate some kind of error term into this
baseline covariate? Thanks a lot.

Graduate student
University of Florida
School of Pharmacy
Department of Pharmaceutics
Office: P4-10
Phone: (352)273-7865
Received on Tue Jul 29 2008 - 16:52:08 EDT

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