Bioequivalence and Bioavailability Forum • Spaghetti & other pasta

Spaghetti & other pasta [NCA / SHAM]

posted by yjlee168 – Kaohsiung, Taiwan, 2013-05-23 22:47 (3983 d 03:49 ago) – Posting: # 10632
Views: 17,235

Dear Helmut,

Wow! That really quite surprises me. I know that all errors may result from "the approximation of trapezoid" (or assumption of trapezoid area between two points) when calculating AUC. Yes, right now we just use line connection between points to plot linear/semilog graphs. From your plots, it looks like lin-up/log-down method is more close to actual AUC. In this case, it does no matter what there is any missing data or not. Lin-up/log-down is more accurate than linear, isn't?

❝ If we use the linear trapezoidal, the semilog plot is wrong. What we are actually calculating would be reflected in the lower right.

❝

❝ [image]

❝

❝ Weird, isn’t it? But then hopefully everybody would realize that the algo overestimates AUCs in the distribution / elimination phase.

Weird indeed but very convincible. Great demo. How do you plot the low-right graph? Is it possible to overlap both the lower-left and the lower-right graph as one plot? That make differences more clear.

❝ Have you ever seen something like this before? I didn’t. Would be a tough job to come up with such a setup in commercial software. :-D

Me either. Why do you think that it would be a tough job for commercial software?

❝ PPS: What do you think about adding rug(t, side=3) to plots in bear?

Should be do-able in bear. But I don't quite understand why you want to add rug() plot? We don't have many data points in each subject (usually less than 50's in each period) for a BE/BA study.

—
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

Complete thread:

handling of missing data gracehung 2013-05-20 07:35
- Lin-up/log-down trapezoidal avoids most trouble Helmut 2013-05-20 14:22
  - Lin-up/log-down trapezoidal avoids most trouble yjlee168 2013-05-22 08:25
    - Multiple peaks: fallback to linear trapezoidal Helmut 2013-05-22 20:25
      - Multiple peaks: fallback to linear trapezoidal yjlee168 2013-05-22 21:57
        
        No interpolation Helmut 2013-05-22 23:25
        
        No interpolation yjlee168 2013-05-23 11:43
        
        Spaghetti & other pasta Helmut 2013-05-23 15:15
        
        Spaghetti & other pastayjlee168 2013-05-23 20:47
        
        Spaghetti & other pasta Helmut 2013-05-23 21:29
        
        Spaghetti & other pasta yjlee168 2013-05-23 22:46
        
        Spaghetti & other pasta Helmut 2013-05-24 01:24
        
        Spaghetti & other pasta yjlee168 2013-05-24 09:17
        
        No interpolation Ken Peh 2013-05-30 19:55
        
        Different algos! Helmut 2013-05-30 22:38
        
        Different algos! Ken Peh 2013-06-03 17:52
        
        Calculate what? Helmut 2013-06-03 18:11
    - Lin-up/log-down trapezoidal example Helmut 2013-05-25 15:09
      - Lin-up/log-down trapezoidal example yjlee168 2013-05-25 19:45
- handling of missing data Ohlbe 2013-05-20 21:45
  - Sorry Helmut 2013-05-21 13:53
    - Sorry gracehung 2013-05-23 01:06
      - Uncertain time point Helmut 2013-05-23 01:35