ISO Standardization and Validation of Reference Testing Methods

—Validation of Alternative Methods in Food Microbiology—

Abstract

Food microbiological analysis is highly variable, given the living status of the analyte and the biological nature of the reagents used. In addition the analytical results are closely related to the method's principle, in particular with conventional Pasteur microbiology and for enumeration methods. Food-borne pathogens represent a direct health hazard for consumer's health. For these reasons, there is a clear need to define common reference methods, properly validated, as well as to get assurance on the quality of commercial test kits which can be used in alternative to these reference methods.
Standardization can be considered to be the preferred mean, since based on consensus, to harmonize reference methods at international level. Standardization structures at international level in ISO and at European level in CEN in food microbiology are at first presented. Some methodological aspects are introduced, as well as the different types of standards developed: reference methods, general aspects. The current programme of work is overviewed. A special hint is given to the position of novel technologies, as well as to the degree of validation of these Standard reference methods.
Reference methods being most of the time based on conventional microbiology, they require a skilled staff and are labor-intensive, long to perform due to the time needed by the bacteria to grow in/on culture media. Thus a large range of alternative methods, based on recent technologies such as ELISA or PCR, have been developed to get results within a shorter interval of time or to reduce work-load through automation. Manufacturers have commercialized a large range of such test kits, but their users need guarantees on their validity, thus the development of validation schemes operated by third-party organizations. To have a common reference technical protocol to conduct these validations, CEN has developed a standard for the validation of alternative methods in food microbiology, adopted by ISO, EN ISO 16140. This standard is presented, as well as its current revision by ISO. The validation/certification schemes are then shortly introduced.
In a final part, we consider the position of Standard reference methods and of validated alternative methods in the context of laboratory accreditation, based on ISO 17025 Standard, and in the European regulatory frame of Regulation 2073/2005 on microbiological criteria in foodstuffs.