Bioequivalence and Bioavailability Forum

Dear All!

No opinions, no answers?

Meanwhile I had attempted to get an opinion from the authors of the Potvin et al. paper (mailed to the correspondence author Walter Hauck). But unfortunately don't got a response up to now.

Let me answer myself
(dropped this from the first post not to prejudice other opinions ):

The decision scheme I have given for the case of 'unsymmetrical' alpha values for the two stages arose from my understanding (?) that the power check step is complementary to the sample size adaptation step.
If we have power >80% (or whatever target power we wish to achieve) the sample size calculation step with alpha₂ (and this is undoubtedly the right alpha value) will give a sample size lower or equal to the size of stage 1. Thus we have no possibility to improve our BE result by raising the number of subjects and have to stay with the stage 1 data.

Now the question is stay with the result 'Not BE' with alpha₁ = 0.005 f.i. or evaluate BE with alpha₂. In my opinion the latter is natural in the light of the BE evaluation if a second stage is necessary.

In case of symmetrical alpha values (f.i. Pocock's alpha₁ = alpha₂ = 0.0294) this new BE evaluation is covered already by the very first BE evaluation and collapses to the result 'Stop: fail' with alpha₂.
This is then the decision scheme B as given by Potvin et al.

Any body out there to prove my point of view wrong?
Any opinion would be highly appreciated!