This document specifies the protocol for the verification of reference methods and validated alternative methods for implementation in the user laboratory.
This document is applicable to the verification of methods used for the analysis (detection and/or quantification), confirmation and typing of microorganisms in:
— products intended for human consumption;
— products intended for animal feeding;
— environmental samples in the area of food and feed production, handling;
— samples from the primary production stage.
This document is, in particular, applicable to bacteria and fungi. Some clauses can be applicable to other (micro)organisms or their metabolites, to be determined on a case-by-case basis.
The technical protocols for the verification of validated qualitative methods and validated quantitative methods are described in Clauses 5 and 6. The technical protocol for the verification of validated alternative confirmation and typing methods is described in Clause 7. The protocols for the verification of non-validated reference methods are described in Annex F.
0.1 The ISO 16140 series
The ISO 16140 series has been expanded in response to the need for various ways to validate or verify test methods. It is the successor to ISO 16140:2003. The ISO 16140 series consists of six parts with the general title, Microbiology of the food chain — Method validation:
— Part 1: Vocabulary;
— Part 2: Protocol for the validation of alternative (proprietary) methods against a reference method;
— Part 3: Protocol for the verification of reference methods and validated alternative methods in a single laboratory;
— Part 4: Protocol for method validation in a single laboratory;
— Part 5: Protocol for factorial interlaboratory validation for non-proprietary methods;
— Part 6: Protocol for the validation of alternative (proprietary) methods for microbiological confirmation and typing procedures.
ISO 17468 is a closely linked International Standard, which establishes technical rules for the development and validation of standardized methods.
In general, two stages are needed before a method can be used in a laboratory.
— The first stage is the validation of the method. Validation is conducted using a study in a single laboratory followed by an interlaboratory study (see ISO 16140-2, ISO 16140-5 and ISO 16140-6). In the case when a method is validated within one laboratory (see ISO 16140-4), no interlaboratory study is conducted.
— The second stage is method verification, where a laboratory demonstrates that it can satisfactorily perform a validated method. This is described in this document (i.e. ISO 16140-3). Verification is only applicable to methods that have been validated using an interlaboratory study.
In general, two types of methods are distinguished: reference methods and alternative methods.
A reference method is defined in ISO 16140-1:2016, 2.59, as an “internationally recognized and widely accepted method”. The note to entry clarifies that “these are ISO standards and standards jointly published by ISO and CEN or other regional/national standards of equivalent standing”.
In the ISO 16140 series, reference methods include standardized reference (ISO and CEN) methods as defined in ISO 17468:2016, 3.5, as a “reference method described in a standard”.
An alternative method (method submitted for validation) is defined in ISO 16140-1:2016, 2.4, as a “method of analysis that detects or quantifies, for a given category of products, the same analyte as is detected or quantified using the corresponding reference method”. The note to entry clarifies that: “The method can be proprietary. The term ‘alternative’ is used to refer to the entire ‘test procedure and reaction system’. This term includes all ingredients, whether material or otherwise, required for implementing the method”.
ISO 16140-4 addresses validation within a single laboratory. The results are therefore only valid for the laboratory that conducted the study. In this case, verification (as described in this document) is not applicable. ISO 16140-5 describes protocols for non-proprietary methods where a more rapid validation is required or when the method to be validated is highly specialized and the number of participating laboratories required by ISO 16140-2 cannot be reached. ISO 16140-4 and ISO 16140-5 can be used for validation against a reference method. ISO 16140-4 (qualitative and quantitative) and ISO 16140-5 (quantitative only) can also be used for validation without a reference method.