Updated standard specifies test method for packaging of terminally-sterilized devices

British Standard to be published giving method for determination of particulate penetration

An effective sterile barrier system is essential to maintain the sterility of terminally sterilized medical devices. BS EN ISO 11607-1 - Packaging for terminally sterilized medical devices — Part 1: Requirements for materials, sterile barrier systems and packaging systems -specifies requirements for materials and pre-formed systems intended for use in packaging systems for terminally sterilized medical devices. BS EN ISO 11607-2 - Packaging for terminally sterilized medical devices — Part 2: Validation requirements for forming, sealing and assembly processes -describes the validation requirements for forming, sealing and assembly processes.

BS EN 11607-1 requires that porous materials used in sterile barrier systems provide an adequate microbial barrier to microorganisms in order to maintain the sterility of the contents.

The standard notes that there is no universally accepted method of demonstrating microbial barrier properties. Evaluation of the microbial barrier properties of porous materials can be conducted by challenging samples with an aerosol of bacterial spores or particulates. The method needs to define a set of test conditions including the flow rate through the material, the challenge to the sample and the duration of the test. The microbial barrier properties of the material are determined by comparing the extent of bacterial or particulate penetration through the material under the specified test conditions. Data from a validated physical test method that correlates with a validated microbiological challenge method are considered acceptable for determining the microbial barrier properties.

BS EN ISO 11607-1, Annex B lists standardized test methods and procedures that may be used to demonstrate compliance with the requirements of the standard. This list includes reference to BS 6256 - Specification for paper for steam sterilization paper bags, pouches and reels for medical use -  in respect of microbial barrier attributes. BS 6256 was published in 1989. BS 6256:1989, Annex C, provided a test method for determination of methylene blue particulate penetration of packaging material. The body of BS 6256:1989 specified requirements for materials, performance, marking and packaging for paper used in the manufacture of steam sterilization paper bags, pouches and reels. These requirements have been superseded by the EN ISO 11607 series and BS EN 868 series of standards. BS EN 868 Parts 2 to 10 - Packaging for terminally sterilized medical devices -specify particular requirements for a range of commonly used materials. This left only Annex C of BS 6256:1989 as being actually current.

The test method in Annex C of BS 6256:1989 is based on a test method described in BS 2577:1955, which is now  an obsolete standard.  BS 2577 was developed to assess the protection afforded by respirator cannisters containing a filtering medium against particulate clouds.  BS 6256:1989 modified the sample holder of the  test equipment in BS 2577 to make it suitable for packaging material. It also normatively referenced BS 3431:1961 – Method for the conditioning of paper and board - which has been superseded by an International standard and withdrawn.

A new edition of BS 6256 is to be published. This new edition contains only the test method from the Annex to the previous edition and retains the same number in order to maintain the integrity of the reference from BS EN 11607-1. The title is changed to Packaging for terminally-sterilized medical devices – Method for determination of methylene blue particulate penetration. The necessary content of BS 2577 has been incorporated into this new edition and the description of the apparatus updated to incorporate metric units. The reference to BS 3431:1961 has been updated to reference BS EN 20187-  Paper, board and pulps - Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samples.

The new edition of BS 6256 brings together in one document and updates the test for particulate penetration of porous material for sterile barrier systems. It will be of interest to manufacturers of packaging for sterile devices and manufacturers of terminally-sterilized devices.

Author: Eamonn Hoxey, of E V Hoxey Ltd, UK, is a writer, trainer and consultant on a range of life science areas including regulatory compliance, quality management, sterility assurance and standards development