Bioequivalence and Bioavailability Forum

Dear Stefano,

❝ My question is the following: if the conditions defined in the FDA GL, the inclusion of the sequence effect is mandatory?

Interesting question. Following Stephen Senn[1] the answer is NO. He is a strong advocat of not testing carry-over in bioequivalence studies. And the inclusion of a sequence effect is effectively a test of unequal carry-over in a 2x2 crossover (its at least one possibility for a significant sequence effect).

But as you have noticed by yourself EMEA and FDA (and other regulatory bodies also) mention the inclusion of sequence in the ANOVA. Also they complain on the other hand that unequal carry over is unlikely (your citation) and should not tested for (EMEA Draft Guideline on BE, line 514 ff).
This is scientifically inconsistent I think. Why to include an effect, that is unlikely to occur and that should not be tested for? But regulatory rules are not always scientifically sound .

Thus, to be on the safe side I would recommend you to perform the usual ANOVA with formulation, period, sequence and subject within sequence as effects. This was my habit up to now, also I am an adept of Stephen Senn's thinking.
If you are a "hero for truth" try to leave the sequence effect out and fight against deficiencies letters .

BTW: Your results concerning the bioequivalence test via the 90% confidence intervals will not be influenced by a decision of including or not a sequence effect in the ANOVA as opposed to Pankaj Mishra's post.
This is because the sequence effect is a decomposition of the between total subject effect into sequence and subject within sequence in the ANOVA. The error MSE is not influenced.

[1] S. Senn, "Crossover Trials in Clinical research", Second edition, Wiley 2002