Pre-use Filter-Integrity Testing: To Test or Not To Test? - Pharmaceutical Technology

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Pre-use Filter-Integrity Testing: To Test or Not To Test?
There is no harmonised guidance on pre-use integrity testing of sterilising filters, prompting discussion among users as to whether such testing is necessary.

Pharmaceutical Technology Europe

For gamma presterilised single-use systems, where the filter manufacturer has already validated that gamma irradiation does not compromise filter integrity, the risk of filter damage during sterilisation appears even more remote. The primary risk of product loss due to integrity failure of gamma-sterilised filters in a single-use filtration system would most probably be from filter damage incurred after sterilisation, for instance, during shipping, handling, and system installation. The lower risk of filter damage and product loss in this case may be further ameliorated if the process is a bulk filtration and, in the event of post-use filter integrity failure, refiltration is qualified and documented in the SOP.

Alternatively, a redundant filtration scheme may be used to minimise risk of product loss in the event of a filter integrity failure discovered only postuse. Finally, the cost of the drug product or process fluid may be sufficiently low that an infrequent disposal is considered inconsequential (e.g., buffers and inexpensive small-molecule drug products).

Although the potential for product loss due to filter nonintegrity may be very low, the effect can be great if the product is expensive and cannot be refiltered, such as with biopharmaceuticals and vaccines. Avoiding catastrophic batch loss, as well as possible product shortages, is a justifiable reason to perform pre-use, poststerilisation filter-integrity testing on single-use filtration systems.

Another advantage of single-use systems compared with stainless steel is that versatile system designs can readily accommodate the necessary flushing to prewet filters before the pre-use integrity test. Stainless-steel tanks for the supply and collection of wetting liquid, which must be cleaned and steam sterilised in place, or autoclaved and aseptically connected, can be easily replaced with preassembled flush supply and collection bags that are gamma sterilised in place. Sterilisation validation is provided by the supplier. Where product is used to prewet the filter for integrity testing, even the side-flush collection bag can be eliminated in some cases. Additional schemes are also available to enable flushing the filter to reduce leachables and any particles that may be present on the downstream side of the filter, along with wetting them for pre-use integrity testing. Filters can be flushed with product to wet the filter, reducing filter leachables and potential particles while recovering the product to maximise yield.

Jerold Martin is senior vice-president of Global Scientific Affairs at Pall Life Sciences, Port Washington, NY (US), and chairman of the Board and Technology Committee at Bio-Process Systems Alliance. Tel. +1 516.801.9086


1. FDA, Sterile Drug Products Produced by Aseptic Processing —Current Good Manufacturing Practice (Rockville, MD, Sept. 2004).

2. EC, Guide to GMP, Annex I — Manufacture of Sterile Medicinal Products (Brussels, Belgium, revised Feb. 2008, effective Mar. 2009).

3. J. Wood, presentation at the IBC Single-Use Conference (San Francisco, CA, Jun. 4–6, 2012).

4. J. Martin, presentation at the IBC Single-Use Conference (San Francisco, CA, Jun. 4–6, 2012).

5. E. Mahajan et al., Pharmaceutical Engineering, 32 (3), 54–56 (2012).

6. K. Lear, presentation at the IBC Single-Use Conference (San Francisco, CA, Jun. 4–6, 2012).


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