Question

Look up SAL (sterility assurance level) and   Define it (essay) and tell how it relates to the field of sterile processing. Does the SAL provide a 100% guarantee of sterility? Can a 100% guarantee of sterility ever be provided?

Answer 1

In microbiology, sterility assurance level (SAL) is the probability that a single unit that has been subjected to sterilization nevertheless remains nonsterile.

It is never possible to prove that all organisms have been destroyed, as the likelihood of survival of an individual microorganism is never zero. So SAL is used to express the probability of the survival. For example, medical device manufacturers design their sterilization processes for an extremely low SAL, such as 10⁻⁶, which is a 1 in 1,000,000 chance of a non-sterile unit. SAL also describes the killing efficacy of a sterilization process. A very effective sterilization process has a very low SAL.

The typical SAL for most devices distributed in Europe and the US is 10⁻⁶  Historically the US permitted a greater SAL value of 10⁻³ for items such as surgical drapes and gowns  However, with the requirement for CE marking at the start of 1998, and in recognition of certain Pharmacopeia requirements, the SAL value decreased to a greater assurance of sterility, 10⁻⁶. This is not to say that a device cannot be submitted and approved by the regulatory authorities with an SAL value greater than 10⁻⁶. Regulatory approval for these lower sterility assurance levels, such as 10⁻³, may be granted if it is shown that the device functionality cannot be achieved with a SAL of 10⁻⁶. Alternatively, if the biomaterials scientists, the microbiologists, and sterilization personnel cannot demonstrate that the device is compatible from a product performance perspective with any sterilization process, they may need to move the product to an aseptic process where contamination rates may not be greater than 0.1%. With either of these scenarios, it must also be shown that the benefits of the device for the target population outweigh the risks (potential harms and severity of these harms to the patient) associated with the use of the device. Another major perceived concern for a greater sterility assurance level such as 10⁻³ is the potential use of the device on elderly patients, immuno-compromised patients, those with HIV, transplant patients, burn patients, newborns, and children. This perception is countered by the fact that these high risk patients routinely are treated with aseptically processed products.