NONMEM Users Network Archive

Hosted by Cognigen

RE: OFV or Diagnostic Plot ?? Which one rules...

From: Nick Holford <n.holford>
Date: Wed, 13 Feb 2019 06:48:56 +0000

Hi Sumeet,
The OFV is often king. But what does the VPC look like? That is the gold st=
andard. Diagnostic plots are equivalent to Rorschach blots.
If you find a way to let us see the VPCs then we can all enjoy the view.
Best wishes,

Holford NHG. The visual predictive check - superiority to standard diagnost=
ic (Rorschach) plots Last accessed 1=
3 Feb 2019. PAGE. 2005;14.
Nguyen TH, Mouksassi MS, Holford N, Al-Huniti N, Freedman I, Hooker AC, et =
al. Model Evaluation of Continuous Data Pharmacometric Models: Metrics and =
Graphics. CPT: pharmacometrics & systems pharmacology. 2017;6(2):87-109.

From: owner-nmusers
 Of Singla, Sumeet K
Sent: Wednesday, 13 February 2019 7:28 PM
To: nmusers
Subject: [FORGED] [NMusers] OFV or Diagnostic Plot ?? Which one rules...

Hi Everyone,

I am fitting two compartment PK model to Marijuana (THC) concentrations. Wh=
en I apply proportional error (or proportional plus additive) residual mode=
l, I get pretty good fits (except 15% of subjects) at all time points.
However, when I apply only additive error residual model, I get perfect fit=
s in all subjects but objective functional value is increased by about 20 u=
nits. DV vs IPRED reveal all concentrations on line of unity.
My question is: should I go with additive error model which gives me perfec=
t fit but higher OFV or should I go with proportional error model which giv=
es me lower OFV but not so good fit in couple of subjects?

Sumeet Singla
Graduate Student
Dpt. of Pharmaceutics & Translational Therapeutics
College of Pharmacy- University of Iowa

Received on Wed Feb 13 2019 - 01:48:56 EST

The NONMEM Users Network is maintained by ICON plc. Requests to subscribe to the network should be sent to:

Once subscribed, you may contribute to the discussion by emailing: