Harmonising the tests for detecting plant pests

The goal of Valitest was to improve diagnostic tools for plant pests such as bacteria, viruses, nematodes and fungi. This detection is essential for taking measures against these harmful organisms as early as possible, both to limit the damage to plants and avoid their dispersion in the environment. Coordinated by ANSES, this project brought together 16 European partners: research organisations, companies producing diagnostic kits, and the European and Mediterranean Plant Protection Organisation (EPPO). Valitest was launched in May 2018 with funding from the European Union's Horizon 2020 research and innovation programme. 

The reliability of diagnostic tests assessed

Central to the project was the validation of pest detection kits. This is important because these tests are currently only validated by the companies that produce them or by a single laboratory. Inter-laboratory validation of the tests is therefore needed to ensure their reliability and determine their performance characteristics (sensitivity, specificity). A large part of the project therefore consisted in conducting inter-laboratory trials to validate the available tests. The performance of 83 tests, designed to detect 11 pests, was assessed. "There is not necessarily such a thing as an ideal test. For example, for a first-line analysis, we could opt for a sensitive but perhaps less specific test, which is effective at detecting the pathogen but could yield false positives. The presence of this pathogen will then be confirmed by a second test." explains Mathieu Rolland, Deputy Head of the Reference Coordination Unit at ANSES's Plant Health Laboratory.

From test kit producers to users

The Valitest project also examined the statistical studies needed to validate these diagnostic tools, the quality and harmonisation of the reference materials used to assess the tests and the assessment of the laboratories' ability to use the diagnostic tests, and sought to identify the expectations of test users, producers and the services for which the diagnostic results are intended. This last point contributed to the choice of priority pests for which an assessment of the diagnostic tests was conducted. The project also led to establishment of the EU association of the Plant Health Diagnostic Industry. This body will aim to bring together diagnostic kit manufacturers to harmonise the quality and performance of the tests produced and promote exchanges with stakeholders and public decision-makers.

The results of the project will mainly be used by the national and European reference laboratories for plant pests. They are the guarantors of the quality of the tests carried out to monitor regulated pests. A book on the methodology used to validate the diagnostic tests is being prepared ("Critical points of TPS organization in microbiology, case study: Plant pathogens" in the book series "Plant Pathology in the 21st Century" - Springer (Publisher) - by the end of 2021).