Revision of the TG/GD

The OECD Test Guidelines Programme (TGP) Secretariat is responsible for periodically revising the compendium of Guidelines and can take initiatives in the revision of existing TGs. The Secretariat may review and reassess the validation status of established test methods for hazard/risk assessment and evaluate potential improvements to an approved test method, for example. Proposals to update (or create) Test Guidelines (TGs) or Guidance documents (GDs) can also be made by the National Coordinators (NCs) of the OECD TGP, the European Commission, industry, non-governmental organisations, and scientific societies (OECD GD 1, as revised in 2009). A proposal for updating a TG or a GD may also come from a Workshop or an Expert Meeting, in the context of the activities of the Chemicals and Biotechnology Committee’s Working Parties, while discussions on the needs for new/revised TGs/GDs may also occur outside the OECD TGP activities, within networks such as the Malta Initiative for testing nanoscale substances, for example. 

The need to make the European Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) regulation enforceable for nanomaterials resulted in the revision and creation of a number of OECD TGs/GDs. See the extension of the revision and new TGs/GDs produced in the NanoHarmony and NANOMET’s status report on OECD TGs and GDs developments for nanomaterials (July 2022) & in the NANOMET Brochure (Sept. 2023).

Other reasons for revision of a TG or GD are listed in the OECD GD 34 (2005) and notably included the reduction in animal numbers or suffering (i.e., consideration of the ‘Replacement, Reduction, Refinement' (3Rs) principle) or any other scientifically justified change to the test method, testing strategy or the associated Standard Operating Procedure (SOP) as leading to:
- equal or more accurate prediction of human health and environmental hazards,
- an increased sensitivity and reliability over an existing test method,
- a broader applicability domain, increased information useful for support of decisions,
- a decrease in cost,
- enhanced ease of use as well as technical problems that became obvious only after implementation of the method (e.g. restricted access to protected elements (OECD GD298, 2019).

Major revisions of a TG (e.g. addition of new endpoints in order to increase the sensitivity of the test method or to address new mechanisms and toxicities) should be submitted as a new independent project to the Working Party of National Coordinators of the Test Guidelines Programme (WNT), in the form of a Standard Proposal Submission Form (SPSF) and go through the Project definition, the Development, the Commenting and approval phases at OECD. As for a new test method, the validation exercises should be sufficiently rigorous to demonstrate unambiguously that the revised test procedure meets or exceeds the performance of the test method to be replaced regardless of whether tests are for chemical properties, human health or environmental effects. Regulatory acceptance is dependent upon the outcome of the validation (OECD GD 34, 2005). Where an existing TG is being updated, the text of the existing version, annotated with the proposed changes, should be included with the draft proposal.

When the changes are deemed minimal and don’t require additional testing and verification, the process of revision can be quicker (e.g. addition or change in references).

• Sometimes it is easier to target the addition of an annexe for a Guidance Document (GD) or the creation of a GD for a Test Guideline than to target the modification/update of an existing document. Seek the support of your National Coordinator and from the OECD secretariat, which has all the institutional memory of the revision process within the OECD Test Guidelines Programme, and will help you refine your revision project.

• Consult the TIPS & TRICKS section of the Pre-OECD phase.

Timelines are the same as for new Test Guidelines or Guidance Documents but depending on the complexity of the proposed revision the entire process can be faster.