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Dr. Harish L. Rao ☆ India, 2009-03-13 05:18 (6301 d 18:24 ago) (edited on 2009-03-13 05:47) Posting: # 3357 Views: 4,899 |
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Dear Group Members, I would like to draw your attention on a potential bug found in Winnonlin 5.2.1 software. Here are the details: During Winnonlin PK data analysis, Lambda_z range needs to be selected. This could be done by one of the following methods: 1. Setting up the Start & End times (terminal phase) or, 2. Manually deselecting points one by one (by holding Ctrl key while selecting or deselecting a point) from a set of all points. Although there were no differences between the two methods in Lambda_z, Half Life, Rsq, Cmax, Tmax, Tlast & Clast values, significant differences were observed in C0 & its related parameters such as, Vz, Vss, AUCINF, MRT, etc. It appears that WinNonlin is doing the log-linear regression with the first two points when no exclusions are applied; however, it is defaulting to the rule of using the first non-zero concentration for C0 when the first two points are excluded. Pharsight Corporation admits that this is a bug & states that a potential fix would be developed in the next release. Until then, it is recommended to use the first option (selection of Start & End times of terminal phase). Best regards, Dr. Harish L. Rao India. |
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SDavis ★★  UK, 2009-03-15 21:35 (6299 d 02:07 ago) @ Dr. Harish L. Rao Posting: # 3368 Views: 3,882 |
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Hi Dr Rao, I'd just like be clear that you should not see this problem with C0 if the recommended method for lambdaz selections is used, i.e. - Single left-click the start point (e.g. 4 hrs) - Hold down the Shift key, and single left-click the end point (e.g. 12 hrs) These steps are sufficient to select the lambdaz range. Alternatively, you can select 'Best Fit' and WinNonlin will use its default algorithm for selecting points for the lambdaz calculation although I personally wouldn't recommend solely this method as I feel it's important to review the actual data and not rely on just a mathematical fit. Simon. — Simon Senior Scientific Trainer, Certara™ [link=https://www.youtube.com/watch?v=xX-yCO5Rzag[/link] https://www.certarauniversity.com/dashboard https://support.certara.com/forums/ |
Ing. Helmut Schütz