What is the difference in Class 5 and Class 6 indicators and which is more appropriate for use in validation of flash sterilisation cycles.

Also, what is the difference in an Emulator and Integrator.
Any help would be appreciated.

Debbie - Australia

This is a question often asked by practitioners and the standard ISO 11140-1 for Chemical Indicators and the guidance ISO 15882 provide some, albeit, very technical, explanations. In summary.

Emulating Indicators
Also known as cycle verification indicators. These indicators are designed to reach an endpoint (eg a specified colour change) when they are exposed to a set of conditions in a sterilizer which are associated with a recognised sterilization process. Thus for example if a steam sterilization process is deemed acceptable (by the local regulatory authorities eg a Pharmacopoeia) after exposure at 134 C for 3 minutes in dry saturated steam then the emulator will reach its defined endpoint when exposed to these conditions. The emulator will have stated values either printed on it or in the accompanying literature explaining its response characteristics. Thus an emulator is normally designed for use in a specific cycle or set of cycles as specified by the stated values. The emulator could be euphemistically termed a "chemical chart recorder". The Emulator provides no information about microbiological inactivation.

Integrators.
Integrating indicators are designed to provide a similar response to that of a biological indicator. Thus the integrator will reach its endpoint (Accept indication) when it has been exposed to a set of conditions which would cause a defined level of inactivation in a defined microbial population. The integrator should also respond to changes in cycle parameters (eg lowering temperatures) in the same way that a BI would. The technical support material supplied with the indicator will describe in greater detail the response characteristics of the indicator and the relationship to microbial kill in a defined microbial population. It should be noted that a true integrator will react to a range of sterilization processes and will provide a response similar to that of a biological indicator exposed to a similar range of exposure conditions.
For this reason Integrator are euphemistically called chemical biological indicators.

Regarding the choice of either integrators or emulators this depends entirely on the the information required by the user. As stated above an emulator will provide information on exposure to a very specific set of cycle conditions. By contrast an integrator will provide information about the microbial killing characteristics of the cycle in which it is used. Thus the time temperature response characteristics will be linked to the response of a defined biological challenge and will change in response to changing cycle parameters in the same way that the BI would. Thus for example if a decrease in temperature along with an extension of exposure time achieves the same level of microbial kill the integrator will reflect this equivalence.

Brian Kirk