What is the acceptable statistical procedure for selection of reserve samples for visual examination

What is the acceptable statistical procedure for selection of reserve samples for visual examination

Hi, normally a statistically sound sample size is not required for reserve samples, since they are not intended to demonstrate or infere batch quality with a specific level of confidence, they are used only as a backup source for a verification testing if needed.

It is a direct regulatory requirement for FDA reguated industries that the selection of reserve samples must be of at least twice as needed to perform all the applicable tests, including visual examination if this is a required test for release.

As stated in CFR 21, part 211.170:
For API:

“The reserve sample consists of at least twice the quantity necessary for all tests required to determine whether the active ingredient meets its established specifications”

For each lot or batch of drug product:

“The reserve sample consists of at least twice the quantity necessary to perform all the required tests, except those for sterility and pyrogens”

I hope this was the information is what you were looking for.

According to my understanding, the question is that how many number batches should be considered and selected for visual examination to be done annually on the reserve samples. Whether should we take all the batches manufactured in one year for visual examination or is there any statistical consideration to calculate a number of batches to be selected for visual examination?

There is no specific criteria given in any regulatory guidelines /requirements for selection of the number batches of a product for visual examination. Based on the number of batches of a product manufactured in a year, batches should be selected for visual examination. One may consider 100% batches for visual examination or as appropriate.