Options summary for each device, its intended use, and potential limitations.
| DESIGN OF |
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| Biological Indicators |
Class 5 Integrating Indicators |
Class 6 Emulating Indicators |
How does this affect my monitoring processes? |
| Biological indicators are designed to demonstrate whether the conditions were adequate to achieve sterilization. Biological
indicators contain a known number of resistant spore-forming microorganisms to
monitor adequacy of the sterilization process. |
Class 5 integrating indicators are designed to react to all critical variables (time, temperature, and the presence of steam) and have Stated Values that correlate to a BI at three time/temperature
relationships. |
Class 6 emulating indicators are designed to react to all critical variables (time, temperature, and the presence of steam) for a specified sterilization cycle. You may hear Class 6 indicators referred to as cycle specific indicators. |
Biological indicators continue to be the highest level of sterilization cycle monitoring and are widely recommended as the preferred monitoring device for releasing loads and monitoring sterilization cycles. If your Sterile Processing Department runs multiple exposure times (e.g. 4, 10 and 18 minutes at 272°F), a distinct Class 6 emulating indicator would be required to monitor each cycle. |
| IMPLICATIONS |
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| Because biological indicators are the only true measure of the sterilization process lethality, they are considered to be the highest level of sterilization cycle monitoring. BI’s are widely recommended as
the preferred monitoring device for releasing loads and monitoring sterilization cycles. |
Class 5 integrating indicators must have three Stated Values at 121°C, 135°C, and at one temperature in between that correlates to a BI. Additionally, the Stated Value at 121°C must not be less than 16.5 minutes. This guarantees the time/ temperature response for a Class 5 integrating indicator will respond like a BI when exposed to ideal, saturated steam. Therefore, if the exposure temperature was not achieved where the Class 5 CI is located in the sterilizer and the BI result was positive (indicating a sterilization failure), the Class 5 CI will respond like the BI and also indicate that a failure had occurred as it mirrors the thermal death rate curve of G. stearothermophilus in the BI. |
Class 6 emulating indicators have one Stated Value for time and temperature for the specific cycle it is designed for.1 There is no requirement for three Stated Values for time and temperature and therefore the response may not correlate to a BI throughout the temperature range. Note that at lower temperatures
the Class 6 response can fall below that of the BI performance (thermal
death rate curve of G. stearothermophilus). |
BI’s provide the only direct measure of sterilization process lethality. Chemical indicators and emulating indicators seek to mirror the death curve of a BI or response at a specific temperature, respectively. Class 5 integrating indicator and Class 6 emulating indicator performance is not tested in poor steam conditions such as superheat or air/steam mixtures. Additionally, CI’s performance compared to a BI is also not tested in these conditions. Because the Class 5 integrating indicator response at lower temperatures parallels the biological response, Class 5 CIs are able to detect the failure condition where the desired exposure temperature is not achieved. This condition is likely to occur when there is:
- incorrect packaging
- incorrect loading
- air/steam mixtures
- an incorrect cycle for load contents
Because the Class 6 response at lower temperatures can fall below the thermal death curve of G. stearothermophilus, the Class 6 emulating indicator can reveal a pass when the BI would indicate a failure. |
1Association for the Advancement of Medical Instrumentation, Sterilization of health care products - Chemical indicators - Part 1: General requirements, ANSI/AAMI/ISO 11140-1:2005.
