Even as International Organization for Standardization (ISO) has come up with ISO 11140-1 standard laying down the general requirements for sterilization of healthcare products for chemical indicators to ensure utmost safety and quality of medicines, a considerable number of pharma units are yet to choose right indicator for sterilization process of their products in the absence of awareness about it, according to biomedical expert Anchal Gupta.

Gupta, a biomedical engineer and director of Yogi Kripa Medi Chem Pvt Ltd said, “Since several years, steam sterilization (autoclaving) is a very popular method used for sterilization in pharmaceutical companies and hospitals. Chemical and biological indicators are widely used to monitor the sterility of the contents being sterilized. ISO 11140-1 defines the general requirements for sterilization of healthcare products for chemical indicators. It specifies performance requirements and/or test methods for chemical indicators intended for use with various sterilization processes.”

The chemical indicators described in this part of ISO 11140 are categorized into six types, viz. type 1 to type 6. The chemical indicators within each of these categorizations are further subdivided by the sterilization process for which they are designed to be used, she said.

Time, moisture and temperature are three important variables for steam sterilization process. The pharma industries can opt for any of the six chemical indicators defined by ISO as per the sterilization process as per the performance characteristics desired, she added.

Type I indicators, called process indicators shall be designed for use with individual items (e.g. packs, containers) to show that the unit has been directly exposed to the sterilization process and to distinguish between processed and unprocessed items. These are intended for use externally, i.e. outside the load pack.

Type 2 indicators (e.g. Bowie- Dick) are intended for use in specific test procedures as defined in relevant sterilizer/sterilization standards. The requirements for specific test indicators and indicator systems are provided in ISO 11140-3, ISO 11140-4, and ISO 11140-5. It is intended for use in special applications, e.g. Bowie and Dick-type test. These are usually used once a day on an empty load and intended for use inside the autoclave machine to check its efficacy. The end result is documented by the user.

Type 3 indicators are internal indicator which are single variable indicator. This indicator only reacts to one critical process variable and will indicate a ‘pass’ condition at a stated value (SV) of the chosen critical variable. These are intended for use inside the pack. These are not popularly used as monitoring only one critical variable may not be helpful for many applications.

Type 4 indicators are internal indicator which is multi variable indicator. This indicator only reacts to more than one critical process variable and will indicate a ‘pass’ condition at a stated value of the chosen critical variables. These are intended for use inside the pack. These are moderately used and usually in conjunction with either Type 5/Type 6 indicators. The tolerance on the test temperature for a Type 6 emulating indicator is -2 °C, and the tolerance on the test time is -25 per cent.

Type 5 indicators are internal indicator, called integrating indicator. This indicator reacts to all critical process variables. The stated values are generated to be equivalent to, or exceed, the performance requirements given in the ISO 11138- series for BIs. The minimum stated value shall be related to the minimum values required to achieve sterilization as specified in International Standards ISO 11135, ISO 11137 (all parts), ISO 17665 (all parts), or by local regulatory agencies. The stated values demonstrate how the indicator integrates over the temperature range. It is intended for use inside the pack. These are commonly used. The tolerance on the test temperature for a Type 6 emulating indicator is -1 °C, and the tolerance on the test time is -15 per cent.

Type 6 indicators are internal indicator?, called emulating indicator. This indicator reacts to all critical process variables for specified sterilization processes. The stated values are generated from process variables of sterilization processes as specified in International Standards ISO 11135, ISO 11137 (all parts) and ISO 17665 (all parts), or by regulatory agencies. It is also intended to use inside the pack. These are commonly used. The tolerance on the test temperature for a Type 6 emulating indicator is -1 °C, and the tolerance on the test time is -6 per cent.

She concluded that all Type 3, Type 4, Type 5 and Type 6 indicators are to be placed inside individual load items and to assess attainment of the critical process variables at the point of placement. Thus, it is clear that chemical indicators are available in different types depending upon the function they are designed for. It is important for the user to select the appropriate chemical indicator for his cycle of steam sterilization in accordance to the performance characteristics desired.