Bioequivalence and Bioavailability Forum

Hi Helmut,

Sorry, because I am lego and I can´t understand all correctly.

❝ There is no ‘R₁’ and ‘R₂’, only one R repeatedly administered in the sequences in different periods. Say, the sequences are TRR | RTR | RRT. Did the CRO call the first administration in each sequence R₁ and the second R₂ (while dropping T)?

Yes. But, although this is not the usual approach, if you set the R treatment as R1 and R2, you can make an R1 / R2 comparison, as if they were different treatments, right? And in this way, Is the 90% CI calculated by the CRO well calculated? It seems to me to be a very large interval for a CV of 20%.

❝ As said above, such a ‘comparison’ will not work.

Why? Can you explain?

❝ You tried CI2CV(lower=0.8731, upper=1.4057, design="2x2x2", n=40), right? That’s not what you have. After recoding (wild guess) you have an Incomplete Block Design. Other degrees of freedom,

Yes, I know, but in any case, the difference should be decimals, not changes from 20% to 70%, right? I can't understand how they get a CV of 20% and I get 70%. What's wrong? Besides, with the CI being so wide, it seems to be much more than 20% CV.

❝ These formulas are for a 2×2×2 crossover and are also implemented in CI2CV(). But again, there is only one R. A ‘PE’ and ‘CI’ doesn’t make sense.

❝ You can only calculate the CV_wR according to the EMA’s or the FDA’s models. The results will be similar, though quite often the one of the FDA is a bit smaller.

But, although this is not the usual approach, if you set the R treatment as R1 and R2, you can make an R1 / R2 comparison, if you want to do it just for curiosity, considering them as different treatments, it will be feasible, right? And in this way, Is the 90% CI calculated by the CRO well calculated? It seems to me to be a very large interval for a CV of 20%. Or mine?

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Edit: Standard quotes restored; see also this post #8. [Helmut]