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-nmus...@globomaxnm.com [mailto:owner-nmus...@globomaxnm.com] On Behalf Of Ethan Wu Sent: Friday, March 20, 2009 6:52 PM To: michael.j.foss...@gsk.com; nmusers@globomaxnm.com 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.foss...@gsk.com" <michael.j..foss...@gsk.com> To: nmusers@globomaxnm.com 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" <bachm...@comcast.net> Sent by: owner-nmus...@globomaxnm.com 20-Mar-2009 09:17 To "'Martin Bergstrand'" <martin.bergstr...@farmbio.uu.se>, "'Ethan Wu'" <ethan.w...@yahoo.com>, nmusers@globomaxnm.com 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-nmus...@globomaxnm.com [mailto:owner-nmus...@globomaxnm.com] On Behalf Of Martin Bergstrand Sent: Friday, March 20, 2009 8:45 AM To: 'Ethan Wu'; nmusers@globomaxnm.com 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.bergstr...@farmbio.uu.se> martin.bergstr...@farmbio.uu.se ----------------------------------------------- Work: +46 18 471 4639 Mobile: +46 709 994 396 Fax: +46 18 471 4003 From: owner-nmus...@globomaxnm.com [mailto:owner-nmus...@globomaxnm.com] On Behalf Of Ethan Wu Sent: den 20 mars 2009 13:05 To: nmusers@globomaxnm.com 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 _____ No viruses found in this incoming message Scanned by iolo AntiVirus 1.5.6.4 <http://www.iolo.com/iav/iavpop3> http://www.iolo.com
