Bioequivalence and Bioavailability Forum 12:53 CET

Main page Policy/Terms of Use Abbreviations Latest Posts

 Log in |  Register |  Search

90% confidence interval for R_dnm [Study As­sess­ment]

posted by d_labes - Berlin, Germany, 2019-01-05 14:01  - Posting: # 19731
Views: 952

Dear Shuanghe,

First: Happy New Year to You and to All.

» Man, I should checked here before I started my work. It could save me a lot of time...
:cool: Late but hopefully not too late insight. As I sometimes stated: All answers (of asked or not asked questions) are here. You only have to dig out what you are interested in.

» Recently I was helping one of my colleagues for dose proportionality study and power model in Smith's article is the preferred method. While I did figured out the "correct" degree of freedom method and reproduce all reported results such as intercept, slope, and 90% CI of those values, ρ1, ρ2, the ratio of dose-normalised geometric mean value Rdnm,..., I could not figure out how Smith obtained the 90% confidence interval for Rdnm (0.477, 0.698).

Can you please elaborate where your difficulties arose? Able to obtain a point estimate of Rdnm but no 90% CI thereof?

» ...
» In his article (pp.1282, 2nd paragraph), Smith wrote that "[i]The 90% CI for the difference in log-transformed means was calculated within the MIXED procedure. Exponentiation of each limit and division by r gave the 90% CI for Rdnm ...

For me this is a dubious description (the whole paragraph) I don't understand at all. Difference in log-transformed means of what?

I would go with the formula of Rdnm

R_dnm = r^(beta1 - 1)
with r= ratio of highest to lowest dose and beta1=slope


Use this with the point estimate of beta1 from your model and its 90% CI limits and you obtain the 90% CI of Rdnm if I'm correct.
Example Cmax in Table 2 of the Smith et al. paper:
beta1 = 0.7615 (0.679, 0.844)
R console:
c(10^(0.7615-1), 10^(0.679-1), 10^(0.844-1))
[1] 0.5774309 0.4775293 0.6982324

Smith reported in Table 2:
    0.577    (0.477,    0.698)
Good enough?

Hope this helps.

Regards,

Detlew

Complete thread:

Activity
 Mix view
Bioequivalence and Bioavailability Forum |  Admin contact
19,032 posts in 4,059 threads, 1,299 registered users;
online 14 (1 registered, 13 guests [including 9 identified bots]).

When a distinguished but elderly scientist states that
something is possible, he is almost certainly right.
When he states that something is impossible,
he is very probably wrong.    Arthur C. Clarke

The BIOEQUIVALENCE / BIOAVAILABILITY FORUM is hosted by
BEBAC Ing. Helmut Schütz
HTML5 RSS Feed