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° s = “Special” indicator (e.g., Bowie-Dick)


° i = “Internal” indica- tor (e.g., CI strip); The table below summarizes these categories accord- ing to their intend- ed use.


TYPE Type 1: “exposure” or process indicator Type 2: indicators for use in specific tests Type 3, 4, 5, 6 “Internal” indicators


Type 3: single critical process variable indicator Type 4: multicritical process variable indicator Type 5: integrating indicator


Type 6: emulating indicator


In addition to selecting a specific type of CI, users need to select a product that is appropri- ate for the method of sterilization they wish to monitor. When labeling chemical indicators, ANSI/AAMI/ISO 11140-1:2014 provides manufacturers with symbols to be used as ab- breviated descriptions of the various steriliza- tion modalities. These symbols help end-users to know at a glance for which sterilization modality a particular chemical indicator is de- signed. Symbols for the methods of sterilization commonly used in U.S. healthcare facilities, and that you may see on chemical indicators and/ or their packaging, include:


Symbol


Process Steam sterilization


Ethylene oxide sterilization


Vaporized hydrogen peroxide sterilization


Another key change in ISO 11140-1:2014 were changes to the performance requirements for Type 1 indicators for steam, ethylene oxide (EO), and vaporized hydrogen peroxide pro- cesses; and to the performance requirements for Type 5 integrating indicators for steam processes and EO processes. To better understand these changes, let’s review a few key definitions. • Critical process variable: “variable identified as being essential to the attainment of steril- ization and monitored by the chemical indi- cator.”1


The standard defines which process


variables are critical for different sterilization processes. For example, time, temperature,


Figure 1: Wrapped pack with steam


indicator tape indicating exposure to the sterilization process


and moisture are listed as critical for steam sterilization; time, temperature, relative humidity, and ethylene oxide concentration are critical for EO sterilization; and time, temperature and hydrogen peroxide con- centration are critical for vaporized hydrogen peroxide sterilization. Steam chemical indicator tests typi- cally include a dry heat test, during


CATEGORY INTENDED USE e1 s2 i


i3 i4 i5


i6


Indicates exposure to a process to allow differentiation between unprocessed and processed items, and/or indicate gross failure of a sterilization process.


For use in special applications (e.g., Bowie-Dick).


Placed inside individual load items to assess attainment of the critical process variable(s) at the point of placement.


Reacts to one critical process variable.


Reacts to more than one critical process variable.


Reacts to all critical process variables. Reacts to all critical process variables.


which the indicator is exposed to dry heat for a specified period of time without reaching its endpoint, to ensure that the indicator requires the presence of steam in order to respond.


• Endpoint: “point of the observed change de- fined by the manufacturer, occurring after the indicator has been exposed to specified stated values.”1


Some chemical indicators have an


endpoint described by a visual change, typi- cally changing from Color A to a distinctly different Color B (e.g., yellow to black). Other chemical indicators have a graduated re- sponse, for example moving front chemical integrators which show a progressive observ- able change to- wards a pass or accept region upon exposure


to critical process variables (see picture above).


• Resistometer: a specialized test vessel capable of reproducible cycles and used by manu- facturers to characterize the performance of chemical indicators, with the exception of Type 2 indicators. The standard states, “Resistometers allow for precise specification and control of the specific test conditions and cycle sequences in order to produce controlled, repeatable studies of the effect of process parameters on indicators. Resis- tometers differ from conventional sterilizers; therefore, if conventional sterilizers are used to attempt to duplicate resistometer condi- tions, erroneous and/or misleading results can occur.”1


• Stated value (SV): “value or values of a critical process variable at which the indicator is de- signed to reach its endpoint as defined by the manufacturer.”1


For Type 3, 4, 5 and 6 indica-


SELF-STUDY SERIES


tors, the standard states that each indicator (or the product label or instructions for use (IFU)) shall be clearly marked with the SVs.


Type 5 integrating indicators for steam sterilization Sterile processing personnel find Type 5 steam integrating indicators particularly relevant and convenient for several reasons, including: • they are the only type of chemical indicator that are designed to react to all critical process variables and for which the stated values are generated to be equivalent to, or exceed, the performance requirements for biological indicators;


• they can be used to monitor a variety of steam sterilization cycles over the entire range of temperatures used in health care facilities. This is because Type 5 indicators have and


are required to be tested at three stated values, 121°C (250°F) and 135°C (275°F) and at one or more equally spaced temperature points in between. Having these three stated values demonstrate how this CI integrates over the temperature range. Manufacturers document the performance of Type 5 indicators in a re- sistometer at the three stated values (at each of which the indicator should reach its endpoint) and at a second set of test points having a temperature 1°C lower and an exposure time 15 percent shorter. At these second test points, the indicator should not reach its endpoint. The revised standard moved this second or failing test point closer to the stated values. In addition, the stated value for Type 5 in- tegrating indicators for steam must be greater than 16.5 minutes at 121°C/250°F and greater than 1.2 minutes at 135°C (275°F).1


As explained


in Annex C of ISO 11140-1, these minimum times link the performance of Type 5 integrating indicators to the minimum requirements for a biological indicator for moist heat sterilization as defined in ISO 11138-3.


Chemical indicators for ethylene oxide (EO) sterilization processes The test and performance requirements for two types of CIs for EO were changed. Type 1 process indicators for EO are tested at a warm and a cool temperature. The 54°C test tempera- ture remains unchanged while the lower test temperature was changed from 30°C to 37°C. Type 5 integrating indicators for EO processes are tested at the same two temperatures, 37°C and 54°C. As with steam integrating indicators, the test time at which the Type 5 integrating in- dicators for EO should not reach their end point was also moved closer to the stated values.


Chemical indicators for vaporized hydrogen peroxide sterilization processes The requirement to test Type 1 process indi- cators designed for the vaporized hydrogen peroxide sterilization processes at 27°C was removed in the new version of the standard. Testing is now done only at 50°C, closer to the See SELF-STUDY SERIES on page 34


www.hpnonline.com • HEALTHCARE PURCHASING NEWS • August 2015 33


Self-Study Test Answers: 1. A; 2. A; 3. A; 4. A; 5. A; 6. B; 7. A; 8. A; 9. A; 10. B.


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