The missing 72h [NCA / SHAM]

posted by d_labes  – Berlin, Germany, 2009-01-27 11:48  – Posting: # 3137
Views: 19,303

Dear Helmut,

» ... I have such a procedure since decades (oh, I’m getting old) in my protocols ...

Don't lose heart! Getting old is not for sissies (Bette Davis) :-D !

I have the vague suspicion that I have not explained my point precise enough.

So let me give an example (real data):
       time      Conc.
----------------------------------
 1     0.0        0.00
 2     0.5        0.00
 3     1.0        2.55
 4     2.0        9.79
 5     3.0       13.23
 6     4.0       14.43
 7     5.0       12.49
 8     6.0       12.78
 9     7.0       10.96
10     8.0       12.40
11    10.0       11.68
12    12.0       11.26        *
13    24.0        8.36        *
14    48.0        7.53        *
15    72.0        4.78 (missing)
----------------------------------


Half live for this curve with no missings is 53.6 h (using points 12-72 h).
AUC(0-72)=584.93 (linear trapezoidal rule for sake of simplicity).

If now the conc. value at 72h is missing unfortunately (vial broken or so), what to do?
AUC(0-48h) is 437.21, considerably lower than AUC(0-72), only 75%.
  1. Option: Exclude subject
  2. Option: Use AUC(0-48)
  3. Option: Extrapolate to 72h (C(calc.)=5.69 using log-lin regression with * points) and calculate then AUC (result=595.85).
Looking forward to your opinion.
Other users also a position?

Regards,

Detlew

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