Assurance of Sterility and Sterility Assurance Levels: What’s in the Future?

Currently there is an initiative in the ISO technical committee on sterilization of healthcare products to develop a standard which discusses assurance of sterility. In the United States we have had an AAMI standard for many years (AAMI ST67) which discusses this topic. As the content of ST67 is adapted for the ISO standard to represent current and future industry thinking worldwide, several topics have been discussed in great detail which are of interest to the sterilization industry. Following is a summary of some of these topics:

1. In the medical device and pharmaceutical industries different terms have been used to describe assurance of sterility. Device has defaulted to sterility assurance level (SAL) and pharma seems to lean toward probability of a nonsterile unit (PNSU). An explanation of this issue will be provided.

2. In discussions regarding assurance of sterility for aseptic processing often there is discussion regarding or a desire to calculate a sterility assurance value. This is not appropriate for aseptic processing as there is not a terminal sterilization process in place. A discussion regarding what is appropriate will be provided.

3. Generally it is still appropriate to maintain the target SAL at 10-6, but there are instances where an alternative SAL is justifiable. An example of this approach will be discussed.
4. Currently there is little to no guidance regarding how much data should be gathered prior to justifying the use of aseptic processing. Some information on what could be considered a reasonable amount of data will be provided.