Bioequivalence and Bioavailability Forum

Dear Imran!

❝ Can anybody suggest me the right formula/method to be used for sample size estimation in BA/BE study.

❝ what I understand that the Boltan suggest sample size estiamtion based on mean and SD.

Are you talking about “Pharmaceutical Statistics” by Bolton and Bon?
Have a look at their table 6.5 (p 169 of the 4th Ed., 2004), which uses the intrasubject CV, the expected point estimate (µt/µR), and the desired power. The original table* served many thousands (!) of BE studies in the last 15 years.
The exact formula is a little bit tricky (see this post), but there are also approximations available (for references see this post).

❝ Some Statistician suggest to use the formula based on intrasubject CV only.

At least for a cross-over study you definitely need the intrasubjct CV (whereas for a parallel study the total variability would suffice).

❝ However it is diffucult many time to get the intrasubjects CV unless u have pilot study data.In such case the sample size estimation using mean and SD will be questinable!!!.

You also may use data from the literature. If the CV is not presented but the ANOVA-table, you may calculate it (from log-transformed data) by$$CV_{intra}(\%)=100\sqrt{e^{MSE}-1}$$If only the Confidence Interval is given, you have to do a little maths (see this post and followings).

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• Diletti E, Hauschke D, VW Steinijans VW. Sample size determination for bioequivalence assessment by means of confidence intervals. Int J Clin Pharm Ther Toxicol. 1991;29(1):1–8.