Bioequivalence and Bioavailability Forum

Minimum AIC?! [NCA / SHAM]

posted by Helmut  – Vienna, Austria, 2008-02-03 14:49 (6347 d 05:50 ago) – Posting: # 1575
Views: 29,436

Dear Ohlbe!

❝ What about Akaike's criterion ?

Minimum AIC is only useful in selecting between rival models (e.g., in PK 1 ↔ 2 compartments, in PD simple E_max ↔ sigmoidal E_max).^*

For the example we get…
+-----+---------+---------+---------+---------+
|  n  |    3    |    4    |    5    |    6    |
+-----+---------+---------+---------+---------+
| AIC |  7.7894 | 12.3142 | 18.3473 | 20.9395 |
+-----+---------+---------+---------+---------+

… which would suggest n=3 as the ‘best’!
Looking at the definition of AIC
   AIC = n × ln (SSQ) + 2p
it’s clear that since in estimating lambda_z the number of estimated parameters p is fixed to 2 (intercept, slope) AIC essentially reduces to a transformation of the residual sum of squares times the number of data points.
AIC is a quite comfortable in compartmental modeling (as compared to the alternative F-test, because no calculations are needed), but in the given problem it does not help.

❝ I think Kinetica uses it, right ?

At least not in the estimation of lambda_z; strange enough there's a parameter ‘G’ in the output, which is neither described in the online-help nor the manual (v4.1.1, 2007).
I will try to find out the next days, what this parameter might be…

---

• Yamaoka K, Nakagawa T and T Uno
  Application of Akaike's Information Criterion (AIC) in the Evaluation of Linear Pharmacokinetic Equations
  J Pharmacokin Biopharm 6/2, 165–75 (1978)

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


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Complete thread:

• Methods for calculation of half lives d_labes 2008-02-01 14:58 
  • Methods for calculation of half lives Helmut 2008-02-01 16:59
    • Methods for calculation of half lives Ohlbe 2008-02-02 23:00
      • Minimum AIC?!Helmut 2008-02-03 13:49
        • G (Kinetica) = R²adj (WinNonlin) Helmut 2008-02-04 01:12
    • Methods for calculation of half lives d_labes 2008-02-04 16:43
      • MAIC and beyond... Helmut 2008-02-04 17:49
  • TTT method Helmut 2008-05-10 13:56
    • TTT method d_labes 2008-05-16 09:12
      • TTT method Helmut 2008-05-16 17:21
        • TTT method d_labes 2008-05-23 15:43
          • TTT method hiren379 2012-07-11 11:11
            • TTT method Ohlbe 2012-07-11 11:37
              • TTT method hiren379 2012-07-11 11:44
                • TTT method Ohlbe 2012-07-11 12:16
                  • TTT method hiren379 2012-07-11 12:53
                    • Eyeball-PK Helmut 2012-07-11 14:37
                      • Eyeball-PK hiren379 2012-07-11 15:28
                        • Eyeball-PK Helmut 2012-07-11 15:47
                          • Eyeball-PK hiren379 2012-07-11 16:24