Levy Dan D, Zeiger Errol, Escobar Patricia A, Hakura Atsushi, van der Leede Bas-Jan M, Kato Masayuki, Moore Martha M, Sugiyama Kei-Ichi
US Food and Drug Administration, Center for Food Safety and Applied Nutrition, College Park, MD, 20740, USA.
Errol Zeiger Consulting, Chapel Hill, NC, 27514, USA.
Mutat Res Genet Toxicol Environ Mutagen. 2019 Dec;848:403074. doi: 10.1016/j.mrgentox.2019.07.004. Epub 2019 Aug 5.
A committee was constituted within the International Workshop on Genetic Toxicology Testing (IWGT) to evaluate the current criteria for a valid Ames test and to provide recommendations for interpretation of test results. Currently, determination of a positive vs. a negative result is made by applying various data evaluation procedures for comparing dosed plates with the concurrent solvent control plates. These evaluation procedures include a requirement for a specific fold increase (2- or 3-fold, specific to the bacterial strain), formal statistical procedures, or subjective (expert judgment) evaluation. After extensive discussion, the workgroup was not able to reach consensus recommendations in favor of any of these procedures. There was a consensus that combining additional evaluation criteria to the comparison between dosed plates and the concurrent solvent control plates improves test interpretation. The workgroup recommended using these additional criteria because the induction of mutations is a continuum of responses and there is no biological relevance to a strict dividing line between a positive (mutagenic) and not-positive (nonmutagenic) response. The most useful additional criteria identified were a concentration-response relationship and consideration of a possible increase above the concurrent control in the context of the laboratory's historical solvent control values for the particular tester strain. The workgroup also emphasized the need for additional testing to resolve weak or inconclusive responses, usually with altered experimental conditions chosen based on the initial results. Use of these multiple criteria allowed the workgroup to reach consensus on definitions of "clear positive" and "clear negative" responses which would not require a repeat test for clarification. The workgroup also reached consensus on recommendations to compare the responses of concurrent positive and negative controls to historical control distributions for assay acceptability, and the use of control charts to determine the validity of the individual test.
国际遗传毒理学测试研讨会（IWGT）成立了一个委员会，以评估现行有效的艾姆斯试验标准，并就试验结果的解释提供建议。目前，通过应用各种数据评估程序来比较加药平板与同时进行的溶剂对照平板，从而确定阳性与阴性结果。这些评估程序包括要求特定的倍数增加（2倍或3倍，具体取决于细菌菌株）、正式的统计程序或主观（专家判断）评估。经过广泛讨论，工作组未能就支持这些程序中的任何一种达成共识性建议。大家一致认为，在加药平板与同时进行的溶剂对照平板的比较中加入额外的评估标准，可改善试验解释。工作组建议使用这些额外标准，因为突变的诱导是一个连续的反应过程，阳性（致突变）和非阳性（非致突变）反应之间的严格分界线没有生物学意义。确定的最有用的额外标准是浓度-反应关系，以及在特定测试菌株的实验室历史溶剂对照值的背景下，考虑相对于同时对照可能的增加。工作组还强调需要进行额外测试，以解决微弱或不确定的反应，通常是根据初始结果选择改变实验条件。使用这些多重标准使工作组能够就“明确阳性”和“明确阴性”反应的定义达成共识，这无需重复测试来澄清。工作组还就比较同时进行的阳性和阴性对照的反应与历史对照分布以确定试验可接受性的建议，以及使用控制图来确定单个测试的有效性达成了共识。
