endogenous compounds [Regulatives / Guidelines]
❝ 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.

❝ 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]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png)
Helmut Schütz
![[image]](https://static.bebac.at/img/CC by.png)
The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes
Complete thread:
- endogenous compounds martin 2017-05-08 19:50 [Regulatives / Guidelines]
- endogenous compoundsHelmut 2017-05-08 21:10
- endogenous compounds martin 2017-05-08 21:19
- endogenous compoundsHelmut 2017-05-08 21:10