To be exact about it, a certificate that reports one test result on one vial extrapolates to claim that all two hundred vials in the lot are identical, which is an assumption worth questioning.
Stratified sampling — testing one vial from the top, one from the middle, and one from the bottom of a shipment — is cheap insurance against segregation.
It helps to be literal here: if the entire lot failed qualification, a retest on a different vial is sometimes done, but reporting a retest result under the same lot number is misleading.
Published data on lot homogeneity from manufacturers who sample multiple vials consistently find variation below the published specifications, suggesting the sampling plans work.
If testing multiple vials, state how many you tested and why you chose those vials.
4Worth flagging that this changed in 2025, so older answers on the site are out of date. – k_szabo 3 months ago add a comment