Class 6 vs. BIs: Can't We All Just Get Along?


Choosing the profession of sterile processing guarantees you never have to attend your child’s career day at school. My daughter asked if I could come to her school and discuss my job. After explaining to her that presenting the complex nature of sterile processing to first graders would probably not be a good idea, she said, “Well, don’t you just wash instruments?” Just wash instruments? Is that really all we do?

In addition to more than 20 years of experience in the field, I have been an instructor for certification preparation for the last seven years. I consistently stress to my staff and students that the one aspect that separates them from dishwashers is sterility assurance. In conducting sterility assurance level (SAL) monitoring; it is our responsibility to utilize all available monitors to provide the highest probability that the instruments processed will not result in a healthcare-acquired infections (HAIs).

There are four basic types of sterilization monitors available for use: Administrative monitors such as policies and procedures, physical monitors such as printouts and gauges, chemical monitors and biological monitors. The intent of this article is not to impart the protocol for appropriate use of each monitor, nor is it to promote any specific brand. The respective manufacturers should be consulted regarding the appropriate use of their monitors. Rather, the objective is to focus on the controversy that has developed between biological indicators and the recently released Class 6 chemical indicators.

Biological indicators (BIs) have been the gold standard for sterility assurance for decades while Class 6 indicators, although used extensively in Europe for more than 10 years, have only been introduced in the United States for the past year. BIs contain live bacterial spores resistant to the respective sterilant while Class 6 indicators are cycle-specific and are designed to react to all the parameters of steam sterilization. They are two different, unique monitors, so why the controversy? The issue is that according to the manufacturer and the Food and Drug Administration (FDA), both monitors can be used for load release.

To understand the confusion, we must first take a step back and ask ourselves, what is the intention of a process challenge device? The purpose is to provide a challenge to the sterilizer to measure if the required conditions or parameters were achieved to afford the highest probability that sterility did occur and thus the load is safe for use.

As reported in a previous article, the independent in-house comparison studies that I performed between BIs and Class 6 verified the manufacturer’s claim that the Class 6 challenge packs measured more of the required parameters then the BIs that I was using. Utilizing aborted cycles, the BI was not able to detect a failed cycle beyond the third pulse prior to exposure phase of the cycle, while the Class 6 detected a failure at 30 seconds’ exposure. According to these results, the Class 6 challenge packs outperformed the BIs in regard to identifying a failed sterilization cycle.

Accepting Change

This is the point where we must step outside the box and be willing to accept that an adequate chemical indicator has been developed that can not only supplement the traditional BI, but it is also capable of providing a greater safety margin. Years ago, event-related sterility and minimally-invasive surgery were unheard of, yet today both are standard accepted procedures. Technological advancements continue to occur for surgical procedures and instrumentation. Why should we not expect, and be willing to accept, that innovated developments will evolve to improve SAL monitoring of these devices? They will occur, they have, and we need to investigate how to appropriately utilize them in our monitoring of sterilization processes.

Although I am obviously a proponent of the Class 6 technology, I need to caution that I am not in favor of the complete elimination of BIs. BIs provide proof that your sterilization process can kill live bacterial spores and should be utilized for sterilizer validation. However, due to the required incubation period, BIs cannot be effectively relied upon for routine load release.

Class 6 indicators do provide an immediate result and also have proven to possess the ability to detect a failed cycle farther into the sterilization process then the traditional BI. In addition, according to the manufacturer, Class 6 challenge packs can detect other steam quality issues such as wet steam, super-heated steam, presence of non-condensable gas and air leaks in the chamber. This information is crucial to diagnosing problems associated with your sterilizer and is not available with the traditional BI monitor. For these reasons, Class 6 challenge packs can and must be used for routine load release. Because of the implementation of Class 6 technology on all steam loads, my department has virtually eliminated load recalls. Any failed sterilization cycle is immediately identified and the instruments never leave the department. Moreover, the Class 6 challenge packs have been able to identify steam quality issues before they result in sterility concerns.

Opposition to Class 6 Technology

Opponents to Class 6 adoption have numerous concerns that need to be discussed. First, they state that since Class 6 indicators are cycle-specific, they cannot be used for extended cycles. Absolutely, Class 6 are cycle specific. Extended cycles are a completely separate issue, one that the industry needs to address, but this situation does not prevent the inclusion of Class 6 challenge packs on other routine loads. In addition, BIs are also not cleared for use on extended cycles, thus this issue is a moot point in regard to comparison of the two monitors. No manufacturers of process challenge devices currently offer a test pack that can mimic the challenge of an extended cycle. Neither Class 6 nor BIs can be utilized for extended cycles.

Opponents also claim that since BIs contain live bacterial spores, they are superior to the Class 6 chemical indicator. My in-house testing proved that our sterilizers were able to kill the spores in the BI even before entering the required exposure phase. Hence, we not did verify that the required parameters for sterility occurred, all we showed was that we need to institute a more difficult challenge since the spores contained in the BI died too easily.

Next, it has been stated that cycle-specific monitors would become too cumbersome and confusing for sterile processing staff. You cannot allow your facility to exclude an innovative advancement in sterility assurance monitoring to be utilized for patient safety simply because you do not want your staff to handle multiple test packs. We currently have multiple test packs for multiple sterilization modalities, e.g., steam, ETO, hydrogen peroxide and peracetic acid. This is not a new issue. In addition, our staff are professionals and need to be expected to function as so. Sterility assurance is too important to not expect our staff to understand the purpose of load monitors and select the appropriate pack.

Opponents further insist that implant loads should contain a BI since these devices will remain inside the body. But they don’t require BIs be used for the instruments. I have a difficult time understanding the justification of this practice. Every sterilization load must have the same standard regardless of content. Incubation periods do not allow BIs to be effective, timely monitors for every load. It is unreasonable and unwise to establish a standard that cannot be followed. Addition of a Class 6 challenge pack on all loads promotes a consistent policy that users can and will adopt.

Finally, opponents have expressed a reluctance to accept Class 6 technology due to the fact that the Association for the Advancement of Medical Instrumentation (AAMI) has not established specific language of Class 6 use in their standards. AAMI is a widely respected standards board and needs to insure that all new devices are thoroughly vetted before establishing recommendations for use. AAMI does, however, specifically state, “As technology progresses, new sterilization process monitoring devices may be cleared by FDA... facilities should rely on the knowledge and expertise of their infection prevention and control, central service and surgical services professionals in the selection and use of process monitoring devices.” Given this statement, waiting until AAMI completes its analysis of Class 6 technology and makes a recommendation as to its appropriate use, would not be prudent in regard to patient safety.


In conclusion, the controversy between BIs and Class 6 needs to end. The issue should also not be a choice between the two. As we have discussed, both monitors need to be included in your sterile processing department’s arsenal of sterility assurance products. The bottom line is patient safety. BIs have served us well over the years and will continue to prove beneficial. However, sterility assurance has never been and will never be an exact science. Technological advancements will continue to occur that will provide a higher SAL for sterilized devices. Class 6 technology is one such advancement and is simply the right thing to do.

Richard P. Blasko is director of materials management/clinical processing at Robinson Memorial Hospital in Ravenna, Ohio.

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