Methods of validation of diagnostic assays for ASFV.

As foreseen in article 6 of Commission Delegated Regulation (EU) 2020/689, the competent authority of each Member State shall ensure that: “The collection of samples, the techniques, validation and interpretation of the diagnostic methods for the purposes of surveillance, shall comply with the specific legislation adopted in accordance with Regulation (EU) 2016/429 and the relevant details and guidance are made available on the websites of the European Union Reference Laboratories (EURL) and of the Commission”.

Any substantial modification of the recommended procedures or submission of new diagnostic tests should be supported by proper validation data confirming that the method is fit for purpose. The WOAH-Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Chapter 1.1.6. – Principles and methods of validation of diagnostic assays for infectious diseases and Section 2.2. – Validation of diagnostic tests), as well as the requirements of the ISO/IEC 17025 provide guidance for validating diagnostic methods to ensure they are compliant with the purpose they are intended for.

A diagnostic method, including commercial method, is considered compliant with the ones recommended by the EURL for ASF if it is:

• A procedure based on a method developed and validated directly by the EURL;
• A procedure based on a method not developed but validated directly by the EURL;
• A procedure based on a method included in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals of the World Organisation for Animal Health (WOAH);
• A method whose sensitivity and specificity have been demonstrated as being effective trhoughout the results obtained in the comparative tests organized by the EURL for ASF;
• A method for which no evaluation has been organized by the EURL-ASF and for which the validation has been done by the National reference laboratories (NRLs) and compliant with the EURL and WOAH guidelines.

 

Method verification.

For standard(ised) methods, such as those validated for the WOAH, EURL, NRLs or commercial kits already validated, validation by the laboratory using the method is not necessary. However, the laboratory needs to verify the performance of the method as detailed in ISO/IEC 17025 Clause 5.4.2: “The laboratory shall confirm that it can properly operate standard methods before introducing the tests”. This is verification. It means that some experimental work must be done to demonstrate that the method works in the end-user’s laboratory. Verification is also required when there is an important change such as a new but similar i.e., extraction methods, equipment, matrix’s, etc. The scope of the Verification Study is to confirm the performance characteristics of the methods, not to reproduce a new complete validation study.

In order to assist the NRLs within the EU on the internal verification of official and alternative ASF diagnostic methods, the EURL for ASF has available a panel of inactivated ASF reference material to provide to the NRLs previous request. The panel of ASF reference material comprises:

• Ten URL-ASF reference serum samples for the evaluation and internal verification of ASF antibody detection techniques.
• Sixteen URL-ASF reference samples for the evaluation and internal verification of DNA extraction methods.
• Twenty one URL-ASF reference DNAs for the evaluation and internal verification of DNA amplification by PCR tests.