Bioequivalence and Bioavailability Forum

Dear All,

Hope you are all well.

A have a question regarding the Sample size determination for in-vitro superiority study.

How to determine the sample size for in vitro study (MIC determination) on clinical isolates to demonstrate synergy against the following bacterial strains involved in causing UTI, SSTI, URTI etc. We have to two drug x and y. And want to prove that x is more superior to y in terms of MIC50.

We had total 11 no. of concentration ranges from 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128 256 of two drug x and y.
We applied these concentrations to 81 strains. We obtain MIC50 on 0.25 for some strains, 0.5 for another some strain and so on out of 81.

For statistical comparison we used convention t-test and for descriptive comparison we use median data.

So is this approach correct to deal with in-vitro study?

Also, there are 10 to 11 subject for each comparison observed. So there may be less accuracy in terms p-value significance. So we are planning to raise the number of population to 500. But how to justify is statistically. Is there any method for in-vitro superiority study?

Thanks.