Bioequivalence and Bioavailability Forum

Dear colleagues,

I know that all people use the following criterion for incurred samples: the difference between original measurement and reanalysis should be lower than 20%. However, the Guideline on bioanalytical method validation has different wording: "The concentration obtained for the initial analysis and the concentration obtained by reanalysis should be within 20% of their mean for at least 67% of the repeats."

What does it exactly mean? For example, if X1=81 and X2=119, their mean is 100, 20% of the mean is 20. So the concentrations are within 20% of their mean if they are within the interval 80-120. Please note that the Guideline does not speak about difference of the measurements, mathematically I understand this statement as two conditions for X1 and X2 that must be fulfilled simultaneously.

I am aware of the fact that my opinion is provocative, but is it wrong?

With best regards,

Jan