Do you still remember exactly when filter integrity testing should be performed?
Background: When exactly should integrity testing be conducted?
Do you still recall whether pre-use testing should be done before or after sterilization?
Post-SIP filter integrity testing provides assurance that the filter was not damaged during the SIP process; however, there are also drawbacks to performing post-SIP pre-use integrity testing. The table below summarizes the potential advantages and disadvantages of conducting pre-use integrity testing before or after SIP.
Pre-SIP / Pre-use Integrity Testing
Advantages | Disadvantages |
Confirms correct installation and integrity of the filter, such as O-rings | Damage to the filter during the SIP process may not be detected until the post-use integrity test |
Confirms the installed filter pore size is correct | The test is time-consuming and duplicates the filter supplier's factory inspection |
Testing can be performed offline to reduce process downtime, and it is easier to test series-connected filter configurations | After steam sterilization, to avoid additional endotoxin contamination, the wetting solution should be controlled at a low bioburden |
The filter wetting process removes soluble components from the filter | Integrity testing of series-connected filters is complex and requires adequate training for operators |
The filter can be dried during sterilization to avoid damage | Requires a special testing area |
Does not compromise sterility assurance (does not affect sterility) | May not meet regulatory expectations in certain special areas |
Post-SIP / Pre-use Integrity Testing
Advantages | Disadvantages |
Reduces the commercial risk of the current batch of product | Usually, performing an integrity test requires the system to provide positive pressure. |
Confirms that the filter and its installation are correct | Shutting down for testing before critical processes, and drying the filter to prevent product dilution |
Performed online | Due to the need for wetting agent removal and gas purging, the downstream requires processing and redesign (increased inlets, more complex), unless wetting with the product itself for integrity testing |
The wetting process of the filter removes all residual soluble components from the filter | Requires installation of integrity test instruments in the clean area (e.g., aseptic filling isolator area) |
— | Series-connected filters require additional engineering design to ensure aseptic assurance between filters. For example: sterile gas must be used, valves installed between filters, and a sterile vent installed on the housing of the secondary filter |
— | Since the filter is also integrity tested before use, it does not increase product safety, but it may increase the risk to the sterile filtrate |