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Performance Testing of Biological Indicators, Class 5 Integrating Indicators and Class 6 Emulating Indicators in Failure Conditions

The purpose of sterilization monitors is to detect situations when sterilization process conditions are not achieved. Sterile processing departments rely on chemical indicators to provide the correct pass or fail result. 3M conducted a study to evaluate the ability of a Class 5 Integrating Indicator and two Class 6 Emulating Indicators to correctly indicate failures to achieve temperatures in some steam sterilization conditions. The results revealed that the Class 6 emulating indicators can incorrectly show a pass result in low temperature failure conditions. In contrast, the Class 5 integrator correctly indicated a fail result in these conditions.

Figure 1: Percent of Class 5 / Class 6 Chemical Indicators Providing a Pass Result When Tested at 121°C (250°F) for 8, 10, 12 and 14 Minutes in a Dynamic-Air-Removal Steam Sterilization cycle

For more information please see "Class 6 Emulating Indicators and Class 5 Integrating Indicators - A comparison of their ability to detect temperature failures within a steam sterilization cycle."

Biological and chemical indicator monitoring products are tested under ideal saturated steam conditions to satisfy both FDA and ISO performance testing requirements. However, a scientific study investigating performance of these monitoring products in suboptimal steam sterilization conditions, (e.g. , superheated steam and incomplete air removal,) reveal that only biological indicators are capable of consistently detecting these types of failure modes.5 Thus, biological indicators will respond correctly by showing positive results under common failure modes, whereas chemical indicators may not.

5AJIC, "Performance of Various Steam Sterilization Indicators Under Optimum and Sub-Optimum Exposure Conditions," Vol. 33, No 5, Supplement 2, June 2005.