NONMEM Users Network Archive

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RE: calculation of AUC

From: Mats Karlsson <mats.karlsson>
Date: Sat, 21 Mar 2009 23:04:58 +0100

Dear Ethan,

 

Just a caution when comparing model-based AUCs with NCA calculated AUCs. =
If you have done your modeling using log-transformation of observations =
and model predictions and then compared AUCs on the linear scale, you =
should not expect a perfect agreement between the two. The reason is =
that the mean of an exponentiated distribution of epsilons is not the =
same as the median, but higher. Thus, the AUCs of model-predicted =
individual profiles will be expected to be lower than either simulated =
or observed. The magnitude of the difference will depend on the residual =
error magnitude and will typically be:

 

%RV expected AUC difference

10 0.50%

20 2%

30 5%

40 9%

50 14%

70 29%

 

Best regards,

Mats

 

Mats Karlsson, PhD

Professor of Pharmacometrics

Dept of Pharmaceutical Biosciences

Uppsala University

Box 591

751 24 Uppsala Sweden

phone: +46 18 4714105

fax: +46 18 471 4003

 

From: owner-nmusers
On Behalf Of Ethan Wu
Sent: Friday, March 20, 2009 6:52 PM
To: Michael.J.Fossler
Subject: Re: [NMusers] calculation of AUC

 

sorry for being lazy this morning and wish relying on others knowledge

just to share, I used DADT=C method, and it didn't depend on sampling =
after I tried with my model (which took quite a while to get results)

-- I could do as Bill suggested setting up some small dataset and simple =
model to check first, then would share with the group ealier :-)


 

 

  _____

From: Michael.J.Fossler
To: nmusers
Sent: Friday, March 20, 2009 9:42:59 AM
Subject: Fw: [NMusers] calculation of AUC


I second Bill's suggestion to work this out on your own for your =
specific problem. This forum can help you with general questions and =
overall approaches, but very specific queries like this are for you and =
your colleagues to hash out.

Error! Filename not specified.
----- Forwarded by Michael J Fossler/PharmRD/GSK on 03/20/2009 09:40 AM =
-----


"Bill Bachman" <bachmanw
Sent by: owner-nmusers

20-Mar-2009 09:17

        


To

"'Martin Bergstrand'" <martin.bergstrand
<ethan.wu75


cc

        

Subject

RE: [NMusers] calculation of AUC

 

                




The easiest answer is to work it out. Do some simulations (without =
variability) with multiple subjects with identical PK parameters BUT =
different sampling times. Tabulate your AUCs and compare the results =
for different sampling times!
  

 

  _____


From: owner-nmusers
On Behalf Of Martin Bergstrand
Sent: Friday, March 20, 2009 8:45 AM
To: 'Ethan Wu'; nmusers
Subject: RE: [NMusers] calculation of AUC
  
Dear Ethan,
  
You need to provide more information on how you plan to calculate AUC =
otherwise the question can’t be answered. It is of course =
possible to calculate the AUC without any influence of the sampling =
frequency. You should be able to find examples of how to do this in the =
NMusers archive. See for example the answer from Mats Karlsson in this =
thread ( <http://nonmem.org/nonmem/nm/98apr032002.html> =
http://nonmem..org/nonmem/nm/98apr032002.html).
  
Kind regards,
  
Martin Bergstrand, MSc, PhD student
-----------------------------------------------
Department of Pharmaceutical Biosciences,
Uppsala University
-----------------------------------------------
P.O. Box 591
SE-751 24 Uppsala
Sweden
-----------------------------------------------
 <mailto:martin.bergstrand
martin.bergstrand
-----------------------------------------------
Work: +46 18 471 4639
Mobile: +46 709 994 396
Fax: +46 18 471 4003
  
  
From: owner-nmusers
On Behalf Of Ethan Wu
Sent: den 20 mars 2009 13:05
To: nmusers
Subject: [NMusers] calculation of AUC
  
Hi all, to calculate AUC of one of the compartments using ADVAN6, if it =
is a fixed time interval, will the AUC be influenced by the frequncy of =
sampling of the dataset within this interval or not?
thanks
  

  _____

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Received on Sat Mar 21 2009 - 18:04:58 EDT

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