[ HOW-TO GUIDE ]
How to Handle a Filter Integrity Test Failure
Respond to a failed pre-use or post-use integrity test on a sterilising-grade filter.
What a how-to is not
A how-to is SPEQ’s practitioner method, not a procedure. It does not replace your own SOP, it is not a validated approach, and the judgement calls in it belong to your quality unit.
A sterilising-grade filter that fails its integrity test may not have delivered a sterile filtrate. EU GMP Annex 1 (2022) sets the testing that should catch this — pre-use after sterilisation, and post-use before the filter leaves its housing — and how a redundant filter is handled. This is how to respond when a test fails.
- 1
Stop and contain
For a pre-use failure, do not filter product: replace the filter and investigate. For a post-use failure, quarantine everything filtered through that filter and do not release it while the investigation is open.
- 2
Rule out a test artefact, with evidence
Check wetting (the wetting fluid and the integrity test specification established in validation), temperature, test equipment, connections and the integrity test procedure. A repeat test is acceptable only under a written procedure that defines when retesting is valid; an unexplained pass on retest does not cancel the first result.
- 3
Use the redundant filter correctly
In a redundant set-up validated to need only one filter, Annex 1 says the backup filter is integrity tested after use only if the primary fails, alongside an investigation and risk assessment into the primary failure.
- 4
Investigate the cause and the batch
Review filter sterilisation and installation, supply and handling, process parameters recorded in the batch record — time to filter a known volume, pressure difference, flow rate, temperature — and the bioburden before filtration. Assess the impact on the batch and on other batches filtered with filters from the same lot or set-up.
- 5
Decide and correct
Record batch disposition with its justification and raise CAPA on the root cause, such as filter handling, sterilisation conditions, installation or supplier quality. If filters were used beyond a validated duration, Annex 1’s controls on maximum duration of use apply.
- !Retesting until a pass is obtained and treating that as the result.
- !Testing the redundant filter first and ignoring the primary failure.
- !Investigating the filter but not the recorded filtration parameters and pre-filtration bioburden.
- !Not considering other batches filtered with the same filter lot or set-up.
How to Handle a Filter Integrity Test Failure: frequently asked questions
Common questions on handle a filter integrity test failure.
When should a sterilising filter be integrity tested under Annex 1?
Paragraph 8.87 says the sterilised filter assembly should be tested before use (pre-use post-sterilisation integrity test), and a non-destructive integrity test should be performed after use, before the filter is removed from its housing.
Can a liquid sterilising filter be reused across batches?
Annex 1 paragraph 8.94 says liquid sterilising-grade filters should be discarded after processing a single batch and not used continuously for more than one working day unless that use has been validated; campaign use needs documented risk assessment, validation and controls on maximum duration (8.95).
Where is bioburden sampled before sterile filtration?
Paragraph 8.93 says bioburden samples should be taken from the bulk product and immediately prior to the final sterile filtration, or before the first filter where a redundant filtration set-up is used.
WHERE NEXT
- DO ITOpen the Deviation & Nonconformance Report template →The structure these steps fill in.
- UNDERSTAND ITFilter Integrity Testing →The principles behind the procedure.
- ALL GUIDESBrowse all 127 how-to guides →
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