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8.4 Alternative SAL
The alternate SAL approach is governed by ISO/TS 19930:2017 [6], and
the recently updated document provides more specificity on the evidence
required to justify using a higher SAL. The alternative SAL approach has
been residing predominantly in the medical device arena and is outlined in
Fig. 8.3. Understanding the material compatibility with the various steril-
ization modalities is the first step.
ISO/TS 19930 provides a framework to systematically attempt to achieve
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a terminal sterilization at 10 SAL. These strategies can be grouped into
improving device compatibility with the sterilant, reducing the exposure
time that the sterilant is in contact with the device, and reducing biobur-
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den, which in turn reduce exposure to reach a 10 SAL. Higher SALs are
considered only after demonstrating that these strategies were ineffective.

8.4.1 Improving device compatibility
Sterilants inactivate bioburden indiscriminately by reacting with any avail-
able functional groups. This reactivity is not limited to the bioburden but
also any susceptible groups on the components of the device itself. The
component functionality after sterilization depends on the component-
sterilant interaction, the criticality of the component, and the stresses and
strains imparted to the component. Alternative component materials should
be considered if the sterilization cycle compromises the function of the
component. Changing materials is significantly easier if the design changes
occur earlier in the program before significant data is generated.
Another strategy to improve device compatibility would be to use an
alternative sterilization modality. Changing materials may not an option
if a given component is critical to the design. An alternative sterilization
modality may be necessary. This topic has been addressed by the FDA in
“Submission and Review of Sterility Information in Premarket Notification
[510(k)] Submissions for Devices Labeled as Sterile: Guidance for Industry
and Food and Drug Administration Staff” [1]. The first step would be an
assessment of Established Category A methods. Category A methods—heat
(dry and moist), ethylene oxide, and radiation (e-beam or gamma)—have
a long history of use in the medical device industries with published con-
sensus standards. Depending on previous experience with the sterilization
modality and the device, this assessment can range from literature searches
to design of experiments to map the design space.