Filter Integrity Testing
Filter Integrity Testing (Bubble Point / Diffusive Flow / Pressure Hold)
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.
Non-destructive physical tests — bubble point, diffusive (forward) flow, and pressure hold — performed on a sterilizing-grade filter before and/or after use to verify that its pore structure has not been compromised, based on a correlation the filter manufacturer establishes between the physical test result and validated bacterial retention.
Because destructively confirming bacterial retention on every filter used in production is impossible, manufacturers rely on a physical surrogate test whose result is mathematically correlated to the retention challenge performed once during filter validation.
Bubble point identifies the pressure at which gas first passes through the largest wetted pore; diffusive flow measures the low-level gas diffusion through the wetted membrane below the bubble point and is more sensitive for larger-area filters; pressure hold detects a pressure drop indicating a gross defect.
A post-use integrity test failure is treated as a potential sterility assurance failure for the associated batch and triggers investigation, since it means the filter’s retention capability during the actual filtration run cannot be confirmed.
- —Physical surrogate for bacterial retention, correlated by the filter manufacturer, not a direct sterility test.
- —Bubble point, diffusive flow, and pressure hold are the three principal test types.
- —Performed pre-use to confirm filter installation and, per Annex 1, post-use wherever feasible.
- —A failed post-use test is a sterility assurance event requiring investigation of the associated batch.
EU GMP Annex 1 (2022); ASTM F838; PDA TR 26
Frequently asked questions
What does Filter Integrity Testing stand for?
Filter Integrity Testing stands for Filter Integrity Testing (Bubble Point / Diffusive Flow / Pressure Hold).
What is Filter Integrity Testing?
Non-destructive physical tests — bubble point, diffusive (forward) flow, and pressure hold — performed on a sterilizing-grade filter before and/or after use to verify that its pore structure has not been compromised, based on a correlation the filter manufacturer establishes between the physical test result and validated bacterial retention.
Which regulations cover Filter Integrity Testing?
EU GMP Annex 1 (2022); ASTM F838; PDA TR 26