Sterility Test
Sterility Test (USP <71>)
What a definition is not
A definition is SPEQ’s plain-language decode of how a term is used in practice, cited to the documents that define it. It is a practitioner reference, not legal or regulatory advice, it does not replace the definition in the source, and where a regulator’s wording differs the regulator’s wording governs.
A compendial test that determines whether a drug product, biologic, or medical device labeled as sterile is free from viable microorganisms. Product units are exposed to microbiological growth media by membrane filtration or direct inoculation, incubated for a defined period under two conditions, and observed for turbidity. It is a mandatory release test for parenteral, ophthalmic, and other products claiming sterility.
Because sterility testing samples only a small fraction of a batch, it is a probabilistic check that complements — never replaces — validated sterilization or aseptic processing controls, container closure integrity, and environmental monitoring throughout manufacture.
Membrane filtration is the preferred method where product is filterable, since it concentrates any organisms present on the filter and rinses away inhibitory antimicrobial residues; direct inoculation is used for products that cannot be filtered.
A positive result triggers a formal laboratory investigation to distinguish true product contamination from a false positive introduced during testing, since the test itself is performed in a Grade A environment and remains vulnerable to operator-introduced contamination.
- —Destructive test performed on a representative sample, not the entire batch — a negative result does not prove absolute sterility.
- —Two principal methods: membrane filtration (preferred for filterable products) and direct inoculation.
- —Requires method suitability (bacteriostasis/fungistasis) validation for each new product formulation before routine testing.
- —A positive result requires an OOS-style laboratory investigation before batch rejection is confirmed.
- —Performed under Grade A conditions within a Grade B background, or in an isolator, to minimize false positives.
USP <71>; Ph. Eur. 2.6.1; EU GMP Annex 1 (2022); 21 CFR 211.167
Frequently asked questions
What does Sterility Test stand for?
Sterility Test stands for Sterility Test (USP <71>).
What is Sterility Test?
A compendial test that determines whether a drug product, biologic, or medical device labeled as sterile is free from viable microorganisms. Product units are exposed to microbiological growth media by membrane filtration or direct inoculation, incubated for a defined period under two conditions, and observed for turbidity. It is a mandatory release test for parenteral, ophthalmic, and other products claiming sterility.
Which regulations cover Sterility Test?
USP <71>; Ph. Eur. 2.6.1; EU GMP Annex 1 (2022); 21 CFR 211.167