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Biological Indicators

Updated: Mar 10, 2022

For Steam Sterilization Load Release or Not?

First, let me say that AAMI's (Association for the Advancement of Medical Instrumentation) minimum recommended use for biological indicators to release routine steam sterilization cycles is weekly but preferably daily. To be clear, the use of biological indicators is to verify the functional operation of the sterilizer. AAMI's guidelines are considered a best practice in the United States. Depending upon your location, if you are only following the minimum recommendations, it leaves a lot of sterilization loads going unchecked by not using a biological indicator. However, many hospitals do run a biological indicator with every load. On the contrary, the United Kingdom does not recommend routine biological indicators for steam sterilization.

In the U.K., the recommendation for testing steam sterilizers occurs periodically at weekly, quarterly, and yearly intervals. The array of recommended tests would be similar to periodic preventative maintenance tests completed by manufacturers in the United States, but the array of tests is more comprehensive than the typical P.M. tests. A baseline is determined during the performance qualification tests for each load, and each load is measured against the baseline before release. We would typically call this process a parametric release.

In the U.S., each sterilization cycle type (e.g., pre-vacuum, gravity) is recommended to be tested utilizing the worst-case scenario; in other words, the shortest exposure time you are utilizing. Biological indicators are also extended to sterilization loads with implantable devices. All implantable loads must contain a PCD (Process Challenge Device). Periodic product quality assurance tests are also recommended, and each cycle should contain biological indicators.

Manufacturers of sterilizers use half-life sterilization cycles (i.e., half the desired sterilization time) to validate sterilizers as required by the FDA. Sterile Processing Departments (SPD) utilize an overkill sterilization process to achieve a sterility assurance level (SAL) of a minimum of 10-6 probability of microbial survival. One of the reasons this level of assurance is utilized is because of the inconsistent nature of sterilization loads in SPD departments.

So why choose to utilize or not utilize biological indicators to release your steam sterilization loads? First, and maybe most importantly, you need to meet the minimum standard for verifying your sterilizers. Secondly, staff competency varies in SPD departments; let's be honest. Lastly, the variation in sterilization loads in SPDs is vast, and almost no load is the same. Whereas in manufacturing, the sterilization load is the same every time.

Does utilizing a biological indicator guarantee that the sterilization cycle is lethal? Yes, but that only means that the conditions were right to achieve sterilization. It does not guarantee that the items in the load are sterile. Many conditions can render an item unsterile. To mention a few:

  1. Recommend sterilization exposure in the IFU (If not followed correctly)

  2. Incorrect loading of a sterilization cart

  3. Incorrect packaging of the item to be sterilized

  4. Bioburden

  5. Improper handling

How you use biological indicators should be decided upon by completing a risk assessment of your processes and conditions in your SPD department. The global steam and hydrogen peroxide biological indicators market size is expected to gain momentum by reaching USD 1,051.4 million by 2028, says Fortune Business Insights. Cost should not be the first consideration when deciding upon whether to use biological indicators or not. However, it can affect your budget's bottom line, especially if you are running a very large SPD department. Patient safety should be first and foremost during your evaluation of need. Do your homework and decide what is right for your organization.

At Evolved Sterile Processing, our consultants have a greater focus on sterile processing. With our decades of experience, we will help you develop better processes and educational resources for your staff.



Health Technical Memorandum 01-01: Management and decontamination of surgical instruments. Part C: Steam sterilization

Med Device Online FDA Issues Final Guidance For 510(k) Devices Labeled As Sterile 1/25/2016

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