RE: OMEGA priors using modes of inverse Wishart matrix
Dear Joachim,
The IW distribution is not something you get from NONMEM, you have to give
the degrees of freedom of the IW prior distribution. Normally this is at or
below the number of subjects in you previous study depending the information
about the parameter per subject.
In addition to User's Guides, you may find useful info in Gisleskog et al J
Pharmacokinet Pharmacodyn. 2002 Dec;29(5-6):473-505.
Best regards,
Mats
Mats Karlsson, PhD
Professor of Pharmacometrics
Dept of Pharmaceutical Biosciences
Faculty of Pharmacy
Uppsala University
Box 591
75124 Uppsala
Phone: +46 18 4714105
Fax + 46 18 4714003
Quoted reply history
From: [email protected] [mailto:[email protected]] On
Behalf Of Joachim Grevel
Sent: 22 February 2012 15:24
To: 'Coen van Hasselt'; nmusers
Subject: RE: [NMusers] OMEGA priors using modes of inverse Wishart matrix
Dear Coen,
There I do have the answer: with MCMC Bayesian in NONMEM 7.1 you have to use
NWPRI according to the guide.
Dear Nidal,
What I try to do is that: use an existing very well defined popPK model
(2500 conc in 200 patients) to obtain individual PK parameters in only 20
additional patients that have sparse sampling (2 to 4 conc per patient). I
was planning to use informative priors rather than add 80 conc to a bulk of
2500 conc. What do you think?
Thanks to all, specifically Tim!
Joachim
From: Coen van Hasselt [mailto:[email protected]]
Sent: 22 February 2012 14:03
To: [email protected]
Subject: Re: [NMusers] OMEGA priors using modes of inverse Wishart matrix
Dear Joachim,
I have always wondered about this particular question myself as well..
Thanks for asking at NMusers.
Another thing related to the PRIORs I was wondering about: you can either
use NWPRI (i.e. with the inverse wishart for OMEGA's), or TNPRI, which uses
a multivariate normal for the OMEGA's. Do you have any idea when to use
either of these two possible implementations ?
Thanks,
Coen
>>> "Joachim Grevel" 02/22/12 2:11 PM >>>
Dear NMusers,
Our NONMEM User Guides are full of good advice and they are searchable. Yet
when I tried to find out whether any of the estimation methods could be
enticed to give me the ?inverse Wishart matrix? needed to specify PRIORS for
OMEGAs, I found no help. Leonid G. mentions the inverse Wishart matrix in
his historic contributions to NMusers, but again I could not find out how to
obtain it. If it does not happen in NONMEM, is there a tool in R that can
give me that matrix?
Your help is greatly appreciated,
Joachim
Joachim Grevel, PhD
Scientific Director
BAST Inc Limited
BioCity Nottingham
Pennyfoot Street
Nottingham, NG1 1GF
Tel: +44 (0)115 8120497