if Clast is zero in bear [🇷 for BE/BA]

posted by yjlee168 Homepage – Kaohsiung, Taiwan, 2015-12-10 18:23 (3030 d 23:08 ago) – Posting: # 15718
Views: 27,395

(edited by yjlee168 on 2015-12-10 18:55)

Dear Astea,

❝ I've got some questions about calculations. Do I understand correctly that BEAR can calculate only AUCall but not AUClast?


No, bear calculates AUC0-last first, then AUC0-inf which is equal to AUC0-last + Clastz (Clast: the last measurable conc., not the last conc.).

❝ What is the formula for AUCinf calculation? I guess it is like AUCinf=AUCall+C/lambda_z, where C is the observed concentration in the last point, so AUCinf is actually AUCinf_obs, based on AUCall, am I right?


:confused: Yes, I guess you're correct if your AUCall is AUC0-last here by definition.

❝ Why does BEAR crash when there is a zero-concentration in the last point? (I change only one point: last point in concentrations of the first subject in the Single2x2x2 demo-data and BEAR returns:


I see. That's because linear regression function (lm) in R cannot allow any y = 0. That's because we take logarithm of conc. (y) first and then do linear regression with log(conc.) vs. time (x). The error is due to log(0).[edited] You should remove the last point that its conc. value is zero; Alternatively, you can input as 'NA' instead of zero. Usually these are the conc. below the lower quantitative limit. They are not really zero, I think.

❝ Error in

❝ lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) :

❝ NA/NaN/Inf in 'y'


❝ It allows calculation only for the manual selection of points.


Not quite correct here. You may not require manual selection for data points if you remove the zero conc. after Tmax or just input as 'NA'.

❝ ...There is no need to calculate lambda_z and AUCinf if we just want to calculate AUC and Cmax...


Agree (in some countries or areas). But most of time, we need to calculate AUC0-inf. Thus, the calculation of lambda_z will be required. BTW, if you just need Cmax and AUC, removing the data points with conc.= 0 will not affect the final results. I will consider to remove the data points with conc.=0 after Tmax automatically in next release.

All the best,
-- Yung-jin Lee
bear v2.9.1:- created by Hsin-ya Lee & Yung-jin Lee
Kaohsiung, Taiwan https://www.pkpd168.com/bear
Download link (updated) -> here

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