NONMEM Users Network Archive

Hosted by Cognigen

Re: OMEGA-Block

From: Hauke Rühs <hauke_ruehs>
Date: Mon, 03 Aug 2009 18:06:04 +0200


Dear NMusers,

thank you for your responses. I parameterized the model by VSS, because
the estimation of the parameter became much better, in terms of
varability, compared to parameterization by V1 and V2.
This is the excerpt from my control stream and output file:


$PK
   CL = THETA(1) * EXP(ETA(1))
   Q = THETA(2) * EXP(ETA(2))
   V1 = THETA(3)* EXP(ETA(3))
   VSS = THETA(4) * EXP(ETA(4))
   V2=VSS-V1

$OMEGA
   0.1 ; OMCL
   0.5 ;OMQ
$OMEGA BLOCK(2)
   0.05 ;OMV1
  0.01 0.05 ;OMVSS


  OMEGA - COV MATRIX FOR RANDOM EFFECTS - ETAS ********


             ETA1 ETA2 ETA3 ETA4

  ETA1
+ 4.08E-02

  ETA2
+ 0.00E+00 4.56E-01

  ETA3
+ 0.00E+00 0.00E+00 2.62E-01

  ETA4
+ 0.00E+00 0.00E+00 -4.34E-02 7.20E-03


Best regards

Hauke




Am 03.08.2009, 16:37 Uhr, schrieb Grevel, Joachim
<Joachim.Grevel

> Hello Hauke,
>
> as always for these specific questions you need to provide us with the
> relevant portions of your control stream and of your output.
>
> Thanks for participating,
>
> Joachim
> _________________________________
> AstraZeneca R&D Charnwood
> Clin. Pharmacology and DMPK
> Bakewell Road
> Loughborough, LE11 5RH
> Tel: +44 1509 644035
> joachim.grevel
>
>
>
> --------------------------------------------------------------------------
> AstraZeneca UK Limited is a company incorporated in England and Wales
> with registered number: 03674842 and a registered office at 15 Stanhope
> Gate, London W1K 1LN.
> Confidentiality Notice: This message is private and may contain
> confidential, proprietary and legally privileged information. If you
> have received this message in error, please notify us and remove it from
> your system and note that you must not copy, distribute or take any
> action in reliance on it. Any unauthorised use or disclosure of the
> contents of this message is not permitted and may be unlawful.
> Disclaimer: Email messages may be subject to delays, interception,
> non-delivery and unauthorised alterations. Therefore, information
> expressed in this message is not given or endorsed by AstraZeneca UK
> Limited unless otherwise notified by an authorised representative
> independent of this message. No contractual relationship is created by
> this message by any person unless specifically indicated by agreement in
> writing other than email.
> Monitoring: AstraZeneca UK Limited may monitor email traffic data and
> content for the purposes of the prevention and detection of crime,
> ensuring the security of our computer systems and checking Compliance
> with our Code of Conduct and Policies.
> -----Original Message-----
> From: owner-nmusers
> [mailto:owner-nmusers
> Sent: 03 August 2009 15:07
> To: nmusers
> Subject: [NMusers] OMEGA-Block
>
>
>
> Dear NMusers,
>
> modelling a 2-compartmet model parameterized by CL, V1, VSS and Q, I got
> to a problem with which I don’t know how to deal with: After choosing my
> structural and statistic model (combined residual error model) I
> estimated
> the covariance matrix by including an OMEGA-BLOCK(4), which reduced the
> OFV by 15. The correlations between the parameters were all estimated to
> be minor (< 0.8). But when I model with a BLOCK(2) on VSS and V1, which I
> would expect to be positively correlated, the correlation is estimated to
> be -0.99. Additionally, the inclusion of BLOCK(2) does not significantly
> improve the OFV.
> So does it, after all, still make sense to include the BLOCK(2)?
> Generally, at which step of model-building would you recommend to test
> for
> parameter correlation?
>
> Thanking you in advance,
>
> Hauke
>
> -----------------------------
> Hauke Rühs
>
> Apotheker
> Pharmazeutisches Institut
> - Klinische Pharmazie -
> An der Immenburg 4
>
> 53121 Bonn
>
> Tel: + 49-(0)228 73-5781
> Fax: + 49-(0)228 73-9757
>
> www.klinische-pharmazie.info
>
>
Received on Mon Aug 03 2009 - 12:06:04 EDT

The NONMEM Users Network is maintained by ICON plc. Requests to subscribe to the network should be sent to: nmusers-request@iconplc.com.

Once subscribed, you may contribute to the discussion by emailing: nmusers@globomaxnm.com.