Changes in Revised ISO 16140

Graph 2. Example of the Accuracy Profile for the validation of quantitative methods.

Image credit: ISO

Another main change is the introduction of the “accuracy profile” study. This study is a combination of testing for bias and precision. The calculations are based on a tolerance interval and evaluation of the data is done using an AL of 0,5 log in the general case. Results are graphically presented as in Graph 2. Results are represented by the middle curve, with below and above the two tolerance intervals and AL are represented by the two fixed dotted lines below and above the observed data.

Transition Between ISO 16140:2003 Version and ISO 16140-2:2016

ISO 16140-2 is substantially different from its predecessor. This will certainly influence the way alternative methods will be validated in the short future but what about the existing validated alternative methods? Publishing a new and improved standard does not necessarily mean that the old way of validation was inapproepriate and that the methods validated according to the former version of the standard are not valid anymore. Therefore, WG 3 has drafted a document endorsed by ISO/TC 34/SC 9, called Guidance on the Transition from ISO 16140:2003 to ISO 16140-2:2016, in order to guide mainly the validation/certification organizations, and as well other involved parties (such as expert laboratories, method developers, regulation bodies) on the implementation of the new ISO 16140-2. This document is an internal ISO/TC 34/SC 9 document, but has been sent to various organizations that are involved in validation of methods, e.g. AFNOR Certification, MicroVal.

ISO 16140-2:2016 has already been used in several validation studies that have been recently finalized or are still in the validation process. No major concerns have been encountered yet with the use of the new validation standard.

Validation in Food Chain Microbiology

As briefly noted earlier, the work of WG 3 is not limited to ISO 16140-2. This group has currently developed two other standards, being ISO 16140-1, Vocabulary, and ISO 17468, Technical requirements and guidance on establishment or revision of a standardized reference method. They have been published at the same time as ISO 16140-2.

In addition, WG 3 is currently working on four other parts of the ISO 16140 series being:

1. Protocol for the verification of reference and validated alternative methods implemented in a single laboratory (Part 3 of ISO 16140);
2. Protocol for single-laboratory (in-house) method validation (Part 4 of ISO 16140);
3. Protocol for factorial inter-laboratory validation for non-proprietary methods (Part 5 of ISO 16140); and
4. Protocol for the validation of alternative (proprietary) methods for microbiological confirmation and typing (Part 6 of ISO 16140).

Part 3, method verification, will especially have a strong impact on all laboratories carrying out analyses in food chain microbiology. Method verification is the study that a laboratory needs to conduct in order to demonstrate its competence in applying a validated method in its own laboratory. Parts 4 and 5 focus on in-house method development/validation and offer new opportunities for laboratories operating in food microbiology testing. Part 6 will provide a technical protocol for the validation of proprietary methods for isolates confirmation, which is also a new concept.

The development of these four standards is still in progress, the versions for the public enquiry (ISO/DIS) will be available in 2017, before the “formal approval”-ballot (ISO/FDIS) probably starts in 2018, where only typing errors can be corrected before the official publication.

in ‘t Veld is convenor of ISO/TC 34/SC 9/WG 3, Method Validation and project leader on ISO 16140 Part 2. Reach him at [email protected]. Sohier is a member of ISO/TC 34/SC 9/WG 3, Method Validation and project leader on ISO 16140 Part 1. Reach her at [email protected]. Mout is secretary of ISO/TC 34/SC 9/WG 3, Method Validation. Reach her at [email protected]. Hardouin is secretary of ISO/TC3 4/SC 9, Food Products—Microbiology. Reach her at [email protected]. And Lombard is chairman of ISO/TC 34/SC 9, Food Products—Microbiology. Reach him at [email protected].