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Sterility Assurance Level (SAL) - A quick intro
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You can submit a number of unprocessed units to a good laboratory to quantify and determine the types of microorganisms present on pre-sterilized products. The frequency of determining bioburden is based on the method of sterilization that you decide to use however it is recommended that at you do this at least monthly or more often. Especially if an out-of-control situation (unusual spike) occurs.
STERILIZATION
Sterilization can occur by various methods. Depending on the nature of the design, material and/or packaging some methods have advantages over others. In all cases the level of sterilization is based on the pre-sterilized bioburden. In some cases the bioburden should influence the sterilization method. For instance there is some cotton that should be sterilized by steam due to the presence of a fungus known as Pyronema domesticum.
When the sterilization method is chosen the method requires validation. The validation method is based on determining the Sterility Assurance Level (SAL). The sterility assurance level can vary depending on the application of the device and is set by various standards and requirements. For invasive products the level is usually 10-6 or 1 in a million. The number 10-6 denotes the number of products that will have a living microorganism following the sterilization process. In other words, once the sterilization is completed the odds of finding an unsterile product will be 1 in a million. As indicated some products are adequate with having a SAL of only 1 in a thousand.
HOW IS SAL DETERMINED?
To explain the way SAL is determined this article will use the example of Ethylene Oxide sterilization.
Let’s say you have a product (like an artificial hip) that requires sterilization. You may start off with a few thousand units – each individually packaged to ensure that the product remains sterile following the process. Depending on the number of products you validate for your sterilization cycle you will have a certain number. In many cases the products will be sent to the manufacturer on pallets (or skids). Each pallet will have a number of cases which are placed on the pallet to a specific configuration.