endogenous compounds [Regulatives / Guidelines]

posted by Helmut Homepage – Vienna, Austria, 2017-05-08 23:10 (2984 d 09:41 ago) – Posting: # 17324
Views: 4,013

Hi Martin,

❝ Several guidelines mention that a negative pre-dose corrected value should be set to zero. However, what about subsequent levels?

❝ I think setting also all concentrations after the first negative to zero would make some sense […] this should be also in-line with guidelines as the method for baseline subtraction needs to be specified a-priori.


Well, this is exactly what I have done for ages. never got a deficiency letter. :-D

❝ PS.: premise of stable endogenous could be verified by looking at adjusted concentrations after the first negative (inclusive) adjusted concentration: should be symmetrically distributed around zero.


Really? You explained that to me so may times; excuse my walnut-sized brain. Baseline (C0) = lognormal. Post-dose (C1) = lognormal. C0–C1 = normal?

C0     <- rlnorm(n=1e6, meanlog=log(1)-0.5*log(0.3^2+1), sdlog=sqrt(log(0.3^2+1)))
C1     <- rlnorm(n=1e6, meanlog=log(2)-0.5*log(0.3^2+1), sdlog=sqrt(log(0.3^2+1)))
C1.adj <- C1-C0
C1.adj[C1.adj < 0] <- 0 # force to zero
mean(C0);sd(C0)/mean(C0)
mean(C1);sd(C1)/mean(C1)
mean(C1.adj);sd(C1.adj)/mean(C1.adj)
summary(C1.adj)
qqnorm(y=C1.adj, col="blue", cex=0.5, las=1)
qqline(y=C1.adj, col="red", lwd=2)


Dif-tor heh smusma 🖖🏼 Довге життя Україна! [image]
Helmut Schütz
[image]

The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes

Complete thread:

UA Flag
Activity
 Admin contact
23,428 posts in 4,929 threads, 1,684 registered users;
59 visitors (0 registered, 59 guests [including 22 identified bots]).
Forum time: 08:52 CEST (Europe/Vienna)

To know that we know what we know,
and to know that we do not know what we do not know,
that is true knowledge.    Nicolaus Copernicus

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz
HTML5