RE: pcVPC or NPDE
Dear Chenyan and Devin,
Chenyan: Nice of you quote me ;) I still stand by the old quote. In my opinion
the advantage with the pcVPC is that it is easy to diagnose if the model
accurately predicts both the central trend as well as the variability of the
data. The NPDEs on the other hand usually makes for a faster diagnostic that do
not require any binning of the data for a rough interpretation. For you own
interpretation I recommend you use both types of diagnostics (possibly with
different x-axis variables, time, dose etc.) and for a publication you should
use whatever you think will be easiest for the audience to interpret.
Devin: The posterior predictive check (PPC) you suggest will only be
appropriate if you have a model that also predicts the dose alteration
decisions (TDM). With TDM dosing a PPC with the actual dosing history will
result in an over prediction of the variability just like VPCs has been
demonstrated to do.
Bergstrand M, Hooker AC, Wallin JE, Karlsson MO. Prediction-corrected visual
predictive checks for diagnosing nonlinear mixed-effects models. AAPS J. 2011
Jun;13(2):143-51. doi: 10.1208/s12248-011-9255-z.
Best regards,
Martin
Quoted reply history
From: [email protected] [mailto:[email protected]] On
Behalf Of Devin Pastoor
Sent: den 11 september 2015 16:46
To: ZhaoChenyan; [email protected]
Cc: [email protected]
Subject: Re: [NMusers] pcVPC or NPDE
Dear Chenyan,
Appropriateness is largely a matter of what the ultimate purpose of the model
is, and neither metric will be 'better' in all cases. Extrapolating into a new
population may require different evaluation diagnostics than using a model to
optimize the dose the observed population.
Given you only have trough samples, using a posterior predictive check on
trough levels or equivalence criteria such as proposed in:
1.
Jadhav, P. R. & Gobburu, J. V. S. A new equivalence based metric for predictive
check to qualify mixed-effects models. AAPS J 7, E523–E531 (2005).
would likely work well.
Devin Pastoor
Clinical Research Scientist, PhD student
Center for Translational Medicine
University of Maryland, School of Pharmacy
On Fri, Sep 11, 2015 at 10:38 AM ZhaoChenyan
<[email protected]<mailto:[email protected]>> wrote:
Dear all:
I'm now having a set of TDM data, only troughs （C0 ） available.
I intend to evaluated the appropriateness of the constructed model.
My question is whether to use pcVPC or NPDE as a diagnostic tool in such a case?
Which one is better?
Or to use them both, as suggested by Bergstrand et al.: "The best practice most
likely lies in using a wide toolbox of diagnostics, rather than one single
universal test to decide whether a model is fit for purpose or not."
Thank you in advance.
Yours,
Chenyan Zhao
Email: [email http://hotmail.com
Mobile: +86 13917430219