National Toxicology Program

For a new or revised test method to be considered validated for regulatory risk assessment purposes, it should generally meet the following criteria (the extent to which these criteria are met will vary with the method and its proposed use).  However, there needs to be flexibility in assessing a method given its purpose and the supporting database.  Because tests can be designed and used for different purposes by different organizations and for different categories of substances, the determination of whether a specific test method is considered by an agency to be useful for a specific purpose must be made on a case-by-case basis.  Validation of a test method is a prerequisite for it to be considered for regulatory acceptance.

• The scientific and regulatory rationale for the test method, including a clear statement of its proposed use, should be available.



• The relationship of the test method's endpoint(s) to the biologic effect of interest must be described.  Although the relationship may be mechanistic or correlative, tests with biologic relevance to the toxic process being evaluated are preferred.



• A detailed protocol for the test method must be available and should include a description of the materials needed, a description of what is measured and how it is measured, acceptable test performance criteria (e.g., positive and negative control responses), a description of how data will be analyzed, a list of the species for which the test results are applicable, and a description of the known limitations of the test including a description of the classes of materials that the test can and cannot accurately assess.



• The extent of within-test variability, and the reproducibility of the test within and among laboratories must have been demonstrated.  Data must be provided describing the level of intra- and interlaboratory reproducibility and how it varies over time.  The degree to which biological variability affects this test reproducibility should be addressed.



• The test method's performance must have been demonstrated using reference chemicals or test agents representative of the types of substances to which the test method will be applied, and should include both known positive and known negative agents.  Unless it is hazardous to do so, chemicals or test agents should be tested under code to exclude bias.



• Sufficient data should be provided to permit a comparison of the performance of a proposed substitute test with that of the test it is designed to replace.  Performance should be evaluated in relation to existing relevant toxicity testing data, and relevant toxicity information from the species of concern.  Reference data from the comparable traditional test method should be available and of acceptable quality.



• The limitations of the method must be described; for example, in vitro or other non-animal test methods may not replicate all of the metabolic processes relevant to chemical toxicity that occur in vivo.



• Ideally, all data supporting the validity of a test method should be obtained and reported in accordance with Good Laboratory Practices (GLPs).  Aspects of data collection not performed according to GLPs must be fully described, along with their potential impact.



• All data supporting the assessment of the validity of the test method must be available for review.
• Detailed protocols should be readily available and in the public domain.
• The method(s) and results should be published or submitted for publication in an independent, peer-reviewed publication.



• The methodology and results should have been subjected to independent scientific review.