Principles of certification

The principles of the certification procedure

The method validation study is carried out in 2 phases, according to the current technical protocol, based on EN ISO 16140.

The objective of the first phase (preliminary study) is to characterise the method and assess its effectiveness by comparing it to the effectiveness of the standardised reference method. This is carried out at the Expert Laboratory. The diversity of samples tested and the experimental conditions applicable to the study (sufficient number of naturally contaminated samples, application of specific stress protocols for artificial contamination…) allow the method to be tested under conditions that are close to the real conditions in the field.

The objective of the second phase (or inter-laboratory study) is to compare the efficacy of the method to be validated and the reference method in several laboratories (8 to 10 minimum) under defined conditions of reproducibility and repeatability.

By combining the results of the 2 phases of the study, it is possible to reach a decision on all of the performance criteria of the method as described in EN ISO 16140.

For each validation study, there are three presentations to the Technical Board of AFNOR Certification:
– draft preliminary study,
– results of preliminary study,
– results of inter-laboratory study.

At each stage, the Expert Laboratory in charge of the validation study presents the application with the manufacturer present. The Technical Board evaluates the application and decides on whether to validate the results. Then at the stage of the results of the inter-laboratory study, a final advice on the certification is given.

The Technical Board consists of twenty or so microbiology experts, some of whom have expertise in statistics. These members represent all the interests at stake in certification: the users of the kits, kit manufacturers and the technical organisations and authorities that use the analytical results. Two members of the Technical Board (the reviewers) are appointed to report in detail on each study and liaise with the Expert Laboratory. Their opinion is given priority during the presentation of results. After the Technical Board has finally approved the validation study, and the contents of the technical instructions for the method to be validated, AFNOR Certification issues the NF VALIDATION mark. A certificate is drafted as well as a summary report of the tests including the main results obtained. These documents may be downloaded on this website.

At the same time, AFNOR Certification evaluates the quality system on the production site of the method to be validated in order to check their effectiveness.


The NF VALIDATION certificate, granted for a 4-years-period, attests that the analytical performances of the alternative method have been certified.

Periodical monitoring

AFNOR Certification carries out regular monitoring in order to check and guarantee users that certified methods comply at all times with the requirements of the NF VALIDATION mark.