Bioequivalence and Bioavailability Forum • Geometric means ± SD

Geometric means ± SD [🇷 for BE/BA]

posted by Helmut – Vienna, Austria, 2016-01-27 14:51 (3432 d 20:53 ago) – Posting: # 15866
Views: 26,752

Hi ElMaestro & Lizhao,

❝ ❝ If I want to plot a mean plot (mean and error bars) of a crossover biequivalence study, should I use within-subject confidence intervals or between-subject confidence intervals?

❝

❝ I think you can plot those curves in any way you want? The BE decision is taken on basis of the CI's.

❝ If you plot Conc versus time and average across subjects then you would often choose to use between-subject variances for error bars.

Between – yes. (m/V)²? Ahem…
I suggest to plot geometric means* ± backtransformed standard deviations. Concentrations likely follow a log-normal distribution. Arithmetic means ± SD can lead to bizarre plots (like this one published by the FDA, page 12 of the PDF).

Having subjects with BQLs leads to trouble. Can be handled in an SOP.
- Calculate the geometric mean if ≥⅔ of subjects at the given time point have concentrations ≥LLOQ and none otherwise, or
- only (!) for the mean plots replace BQLs with LLOQ/2.
An alternative is the median and 25/75 percentiles.

—
Dif-tor heh smusma 🖖🏼 Довге життя Україна!
Helmut Schütz

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

Complete thread:

R code for analyzing classical 2X2 crossover designed bioequivalence data lizhao 2016-01-22 00:13
- R code for analyzing classical 2X2 crossover designed bioequivalence data ElMaestro 2016-01-22 00:59
  - R code for analyzing classical 2X2 crossover designed bioequivalence data lizhao 2016-01-22 01:26
    - On random effects and bogus statements ElMaestro 2016-01-22 12:13
      - FDA 'own' SAS code for 2x2 d_labes 2016-01-27 09:57
        
        FDA 'own' SAS code for 2x2 nobody 2016-01-27 10:09
        
        OT: PM to ElMaestro Helmut 2016-01-27 13:39
        On coffee and such... ElMaestro 2016-01-27 13:47
      - Geometric means ± SDHelmut 2016-01-27 13:51
        
        Geometric means ± SD nobody 2016-01-27 15:20
        
        Money makes the world go ’round Helmut 2016-01-27 16:11
        
        Money makes the world go ’round nobody 2016-01-27 16:31
        
        Fixed or random effect kumarnaidu 2016-11-04 14:05
        
        PROC GLM fixes Subject mittyri 2016-11-04 23:00
        
        PROC GLM fixes Subject kumarnaidu 2016-11-05 05:22
        
        PROC GLM fixes Subject mittyri 2016-11-05 10:13
        
        PROC GLM fixes Subject kumarnaidu 2016-11-07 06:24
        
        PROC GLM fixes Subject mittyri 2016-11-07 11:57
        
        PROC GLM fixes Subject kumarnaidu 2016-11-07 12:42
        
        Geometric means ± SD Ben 2016-11-08 21:20
        
        Misunderstanding Helmut 2016-11-09 15:29
        
        Misunderstanding Ben 2016-11-14 19:40
        
        RTFM Helmut 2016-11-14 21:50