Bioequivalence and Bioavailability Forum

Hi all,

I have a silly question with regard to the number of samples need for ISR according to EMA's guideline. I think it's probably more of problem of "understanding English expression".

The guideline says: "The extent of testing depends on the analyte and the study samples, and should be based upon in-depth understanding of the analytical method and analyte. However, as a guide, 10% of the samples should be reanalysed in case the number of samples is less than 1000 samples and 5% of the number of samples exceeding 1000 samples."

What I understood the phrases, with a bit common sense, is that if we have many samples in a BE study ("many" here means > 1000) then we can choose only 5% of the total samples for ISR. If we do not have that many of samples in a study ("not that many" here means < 1000) then we have to choose 10% of total samples for ISR.

However, all CROs I've worked with in India understood it as "10% of the first 1000 samples plus 5% of the remaining samples".

So if we have 2200 samples in total, my understanding is 2200x5%=110 samples for ISR but CROs will request 1000x10%+(2200-1000)x5%=160 samples.

It probably is not that important from economic perspective since the price will differ very little but this question nagged me for quite some time now I'd like to hear other forum members' opinion.