Reprocessing- Do You Have Confidence In Your Instrument Sterility?

When doing reprocessing, it can be difficult to know exactly what to do to ensure that you have the highest degree of confidence about the sterility of your instruments. One of the things we see a lot of confusion about is the use of Class 5 indicators. Should they be in every pouch and cassette? Should they be in PCD? What if I have a 24-minute biological indicator, do I still have to use a Class 5? Do I have to keep the test strip? Well, that all depends…


Before we dive into the details, it is important to understand what chemical indicators tell us. There are several classes of indicators that provide different amounts of information. The ones we will talk about here are class 1, which simply say that the indicator has been exposed to the sterilization environment, class 4, which say that at least 2 sterilization parameters have been met, and class 5, which respond to all three physical parameters (time, pressure, and temperature). It is important to remember that just because a class 5 indicator responds to the cycle appropriately, that does not mean that your cycle is good to go. All the quality assurance and checks you do work together to provide confidence that your sterilization cycle was successful. Now to determine which ones you need!


The first thing to check: do you have a sterilizer with a recording method? This is usually done using a USB, data recorder, or a printout, although some models save directly to the cloud. If you don’t have this, you are required to periodically check the physical parameters as the cycle progresses and document them. Your chemical indicators requirements would be that every package in every load has a minimum of a class 1 external indicator and a class 5 internal indicator. If you do have a recording method, the next thing to decide whether you will be able to quarantine.


Quarantining instruments is the expectation, however, it is not always possible due to certain constraints. If quarantining is occurring, then only the standard class 1 external and class 5 internal chemical indicators are needed. If it is not possible, then the incubation period for your BI is the next thing to consider.


How long does your biological indicator take to incubate? If it takes 24 hrs, then you have 2 options: you can either include a class one external and class 5 internal indicator in every pouch and cassette, or you can place a class 5 in a process challenge device (PCD) and have every package contain a class 1 external and class 4 internal. If you have a biological indicator with a shorter incubation time, you have a little more flexibility. While it is still best practice to use a class 5 in a PCD, you are only required to have the external class 1 and internal class 4 after you know that the BI test was successful.


That is a lot of words, so I have made a handy flowchart to help simplify things.

In general, every package must have a minimum of a class 1 external indicator (typically built into pouches, added to cassettes in the form of autoclave tape) and a class 4 internal indicator (typically built into pouches, added to cassettes in the form of a test strip). Lastly, while it (almost) never hurts to keep a physical record of test results, the class 5 test strips do not typically need to be kept. A good sterilization log asks specifically about chemical indicators, and the person validating the load and signing off that everything is acceptable is verifying that the test strip was also successful.


Happy sterilizing!


Portia completed her Honours BSc in Biology with a minor in Chemistry from Wilfrid Laurier University, and after working for a couple years, she returned to school to study Advanced Biotechnology at Durham College and earned an Ontario College Advanced Diploma. She is currently earning a Masters degree in Infectious Disease at The London School of Hygiene & Tropical Medicine in London, England, has completed her Associate of Infection Prevention and Control certification, and is working towards obtaining her CIC designation. Both of these are continuing to expand her knowledge of effective infection control and the ways the principles can be applied to practical measures. Having always had an interest in the science of healthcare, and with previous roles related to safety and quality control, Portia brings experience in leadership, education, and continuous improvement. Portia’s expertise pertains to Dentistry and Oral surgery, and she is a qualified fit tester. She also has experience in health care construction and renovation with knowledge in various design standards including the CSA Infection Control During Construction and Renovation (Z317.13-12) and Canadian Healthcare Facilities (Z8000).