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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 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



"'Martin Bergstrand'" <martin.bergstrand




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 ( <> =
Kind regards,
Martin Bergstrand, MSc, PhD student
Department of Pharmaceutical Biosciences,
Uppsala University
P.O. Box 591
SE-751 24 Uppsala
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?


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

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