Normative references (MODIFIED)
ISO 11140-1:2014 has updated the list of normative references to reflect current editions of standards and standards that have replaced some that were previously listed.
3 Terms and definitions (MODIFIED)
There have been a number of terms that have been modified, either to make them more intuitive, or to prevent confusion with other terms used within the ISO/TC 198 standards on sterilization.
For example, the term ‘critical variable’ has been modified to ‘critical process variable’ in order to make it clear that these are variables that may be detected by the indicator, rather than being critical variables of the sterilization method. The definition of the term ‘indicator’ has been changed from meaning the indicator in the form intended to be used, to the actual printed indicator that may be subsequently incorporated into a pack or barrier system; for example, an assembled single use Bowie-Dick test device was formerly referred to as a whole as an indicator, whereas the whole device is now referred to as an indicator system, with the test sheet within referred to as an indicator. This particular example is aided by a diagram in Annex E. The use of the more intuitive terms should aid in the interpretation of the standard by users of chemical indicators, should they read ISO 11140-1:2014.
4 Categorization (MODIFIED)
The former edition of ISO 11140-1 described indicators using a numerical classification; the term class has been replaced by the term type so as not to infer any hierarchical significance to each of the classes. In the 2005 edition, these were classified according to their intended use, however, Types 3, 4, 5 and 6 have arguably the same intended use, i.e. as an internal indicator to verify attainment of process parameters. The 2014 edition highlights this by describing three functions of a chemical indicator – differentiation of unprocessed from processed items, specific tests such as the Bowie-Dick test, and verification of the attainment of process parameters. In addition, Table 1 describes this in more detail, based on intended use, type and category. The term category refers to the use of an optional descriptor in front of the numerical categorisation; these prefixes may be e, for exposure, s for special, or i for internal. This has labelling implications for manufacturers of chemical indicators, and may cause initial confusion amongst the user community, albeit in a limited way, as the numbers will remain similar to prior editions of ISO 11140-1.
In addition to the use of the term type instead of class, Type 3 and 4 indicators have been renamed from single variable indicators and multi-variable indicators to single critical process variable indicators and multicritical process variable indicators, respectively.
5 General requirements (MODIFIED)
The general requirements are largely unaltered in the 2014 edition; subclause 5.8 (labelling) has been reorganised to flow better, and there is recognition that an EU authorized representative address may be needed on the product labelling. A new symbol has been introduced in subclause 5.10 which is designed to alert users of the need to use indicators with a specific test load if intended by the manufacturer. This will require manufacturers of such devices to affix this symbol onto these indicators, and will require users to be educated to its meaning.
6 Performance requirements (MODIFIED)
There have been few significant changes to Clause 6, as the changes in the performance requirements have been specified in Clauses 8, 10, 11 and 12.
7 Test methods (MODIFIED)
The majority of the test methods remain unchanged in Clause 7, however subclause 7.3.3 a) does now require the initial evacuation of the resistometer to 4.5 kPa (the 2005 edition allowed manufacturers to use different vacuum levels if this was stated on the instructions or labelling of the indicators) and to achieve this within 60 seconds (previously this had to be achieved within 2 minutes). This may have implications for manufacturers who have test equipment not capable of meeting these requirements (performance requirements for resistometers are specified in EN ISO 18472).
8 Additional requirements for process (Type 1) indicators (MODIFIED)
There have been small changes to the performance requirements for Type 1 indicators for steam, Type 1 indicators for EO and Type 1 indicators for vaporized hydrogen peroxide (VH2O2). Whilst these are small changes, existing manufacturers may need to type-approve their current indicators and change their methods for testing indicators so they are consistent with those in the 2014 edition of ISO 11140-1. These changes are as follows:
The revised performance requirements for Type 1 indicators for steam are given in Table 2 of ISO 11140-1:2014 (subclause 8.2); the fail condition has been changed from 3 minutes at 121 °C, to 2 minutes at 121 °C, and the pass condition remains at 10 minutes at 121 °C. The fail condition has been changed from 0.5 minutes at 134 °C, to 0.3 minutes at 134 °C, and the pass condition remains at 2 minutes at 134 °C.
The revised performance requirements for Type 1 indicators for EO are given in Table 4 of ISO 11140-1:2014 (subclause 8.4); the fail condition has been changed from 5 minutes at 30 °C, to 3 minutes at 37 °C, and the pass condition has been changed from 30 minutes at 30 °C, to 25 minutes at 37 °C. These changes reflect the discontinued use of resistometers at the test condition of 30 °C and prevalent use at 37 °C.
The revised performance requirements for Type 1 indicators for VH2O2 are given in Table 7 of ISO 11140-1:2014 (subclause 8.7); the pass and fail conditions at 50 °C have not been changed, however the performance requirements at 27 °C have been removed, as there are no sterilizers available that work at 27 °C, hence there should be no user implications. This could, however, have implications for manufacturers of indicators making claims for a previously termed Class 1 indicator working at 27 °C, as all claims for conformity to ISO 11140-1:2014 for a Type 1 indicator for VH2O2 will now have to be completed at 50 °C only.
10 Additional requirements for multicritical process variable (Type 4) indicators (MODIFIED)
There have been no performance requirement changes for Type 3 and 4 indicators in Table 8, however additional performance requirements for Type 4 indicators for VH2O2 have been added.
11 Additional requirements for steam integrating (Type 5) indicators (MODIFIED)
Perhaps one of the biggest single changes to the 2014 edition of ISO 11140-1 is the change to the performance requirements for Type 5 indicators for steam. The 2005 edition allowed a comparatively large difference in performance between the fail and pass conditions; this large performance window has been significantly narrowed from 36.4 % down to 15 %. A minimum performance at 135 °C of 1.2 minutes is also specified. The indicator temperature coefficient range has been changed (and significantly widened) from not less than 6 °C and not more than 14 °C, to not less than 10 °C and not more than 27 °C. The requirements for steam indicator performance in dry heat have also been changed; the 2005 edition required no change when exposed to 137 °C + 1 °C - 0 °C for 30 minutes; this has been changed to 140 °C ± 2 °C for 30 minutes. Manufacturers of Type 5 indicators may need to re-type test their indicators and change their release testing requirements as a consequence of these changes. These changes are likely to be subtle from a user perspective, however they seek to enhance the performance of Type 5 indicators, thus increasing patient safety.
These performance requirements have been editorially reformatted into tabular format and expressed in Table 9.
NOTE Clause 12 from ISO 11140-1:2005 (REPLACED)
This clause and performance requirements relating to Type 5 indicators for dry heat have been removed from the 2014 edition of ISO 11140-1. Deletion of this clause has caused the subsequent clauses to be misaligned to the clauses in the previous edition.
12 Additional requirements for ethylene oxide integrating (Type 5) indicators (MODIFIED – formerly Clause 13)
Significant changes have been made to the performance requirements for Type 5 indicators for EO; the minimum performance requirements for the pass condition have not changed at 54 °C, however the minimum performance requirements at 37 °C have been changed from 90 minutes to 75 minutes. This will allow manufacturers to develop Type 5 indicators for EO processes that reach their end point much quicker.
The performance requirements for the fail condition for Type 5 indicators for EO have been changed; their performance window in the 2005 edition allowed a comparatively large difference in performance between the fail and pass conditions; this large performance window has been significantly narrowed from 33.3 % down to 20 %.
Manufacturers of Type 5 indicators may need to re-type test their indicators and change their release testing requirements as a consequence of these changes. This is likely to have little, if any, consequences for end users of these indicators.
These performance requirements have been editorially reformatted into tabular format and expressed in Table 9.
13 Additional requirements for emulating (Type 6) indicators (MODIFIED – formerly Clause 14)
There have been no significant changes to the performance requirements for Type 6 indicators, with the exception of Type 6 indicators for steam, where the dry heat test that is used to ensure that steam is required for a colour change, has been modified. The 2005 edition of ISO 11140-1 required a dry heat temperature of 137 °C + 1 °C - 0 °C, whereas the 2014 edition requires testing to be conducted at 140 °C ± 2 °C.
Annex C Rationale for the requirements for integrating indicators and the link to the requirements for biological indicators specified in ISO 11138 (all parts) and microbial inactivation (MODIFIED)
Annex C is an informative annex that is designed to provide a rationale for the performance requirements of Type 5 indicators; changes have been incorporated into this annex based on the changes to Type 5 indicators for steam and EO. This includes the addition of a graph that attempts to justify the change in the requirements for the temperature coefficient of a Type 5 indicator for steam.
Annex E Relationship of indicator and indicator system components (MODIFIED)
Annex E is another informative annex, and seeks to show the inter-relationship of the terms used to describe indicators, indicator agent, substrate, specific test load and indicator system. It supports the terms and definitions used in Clause 3.
Reviewers This commentary was peer reviewed by: Adrie de Bruijn, National Institute of Public Health and the Environment (RIVM), Gary Cranston, MS PCS, Inc
Disclaimer This commentary is commissioned text from expert authorities in their industry. It has been commissioned, edited and peer-reviewed before publication but remains the personal opinion of the individual experts who have provided it. It is not official British Standards guidance. Accordingly, BSI cannot accept liability for any direct or indirect loss or damage arising from a reliance on the commentary except to the extent that such liability may not be excluded by law.