Reduction of misleading (“false”) positive results in mammalian cell genotoxicity assays. II. Importance of accurate toxicity measurement
Abstract
In a previous publication, Fowler et al. [4] demonstrated that the seemingly high rate of false or misleading positive results obtained in in vitro cytogenesis assays for genotoxicity - when compared with in vivo genotoxicity or rodent carcinogenicity data - was greater when rodent cell lines were used that were also reported to have mutant or non-functional p53. As part of a larger project for improvement of in vitro mammalian cell assays, we have investigated the impact of different toxicity measures, commonly used in in vitro cytogenetic assays, on the occurrence of misleading positive results. From a list of 19 chemicals that produce "false" positive results in in vitro mammalian cell assays [10], six substances that had given positive responses in CHO, CHL and TK6 cells [4], were evaluated for micronucleus induction in vitro, with different measures of toxicity for selection of the top concentration. The data show that estimating toxicity by relative cell count (RCC) or replication index (RI) consistently underestimates the toxicity observed by other measures (Relative Population Doubling, RPD, or Relative Increase in Cell Count, RICC). RCC and RI are more likely to lead to selection of concentrations for micronucleus scoring that are highly cytotoxic and thus could potentially lead to artefacts of toxicity being scored (elevated levels of apoptosis and necrosis), generating misleading positive results. These results suggest that a further reduction in the frequency of m…
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Toxicity measures such as relative cell count or replication index may underestimate cytotoxicity compared to RPD or RICC, potentially leading to selection of excessively cytotoxic concentrations and misleading positive results.
“This conclusion is supported by Fowler et al., who demonstrated that toxicity measures such as relative cell count or replication index may underestimate cytotoxicity in comparison to RPD or RICC. This can lead to the selection of excessively cytotoxic concentrations for micronucleus scoring, thereby increasing the risk of misleading positive results caused by toxicity-related artefacts (Fowler et”
From Cytotoxicity across OECD methods is not a single endpoint: context-dependent roles, variability and implications for decision-making (2026) · cites this paper as Fowler et al., 2012
In mutagenicity testing, excessive cytotoxicity or cytostasis may cause misleading positives through oxidative stress, nuclease activation, impaired DNA repair, disturbed cell-cycle progression, chromosomal mis-segregation or selective survival of damaged cells.
“In mutagenicity testing, excessive cytotoxicity or cytostasis may cause misleading positives through oxidative stress, nuclease activation, impaired DNA repair, disturbed cell-cycle progression, chromosomal mis-segregation or selective survival of damaged cells (OECD, 2012,2016,2023; Fowler et al., 2012; Azqueta et al., 2022).”
From Cytotoxicity across OECD methods is not a single endpoint: context-dependent roles, variability and implications for decision-making (2026) · cites this paper as Fowler et al., 2012
Such practices are consistent with GIVIMP principles and with guidance emphasizing accurate toxicity measurement to avoid artefactual outcomes.
“Such practices are consistent with GIVIMP principles and with guidance emphasizing accurate toxicity measurement to avoid artefactual outcomes (Fowler et al., 2012; OECD, 2025f,2005).”
From Cytotoxicity across OECD methods is not a single endpoint: context-dependent roles, variability and implications for decision-making (2026) · cites this paper as Fowler et al., 2012
Cited by
Sorted by citations
Reisinger, K., Blatz, V., Brinkmann, J., Downs, T. R., Fischer, A., Henkler, F., Hoffmann, S., Krul, C., Liebsch, M., Luch, A., et al. (2018) · Mutation Research/Genetic Toxicology and Environmental Mutagenesis · doi:10.1016/j.mrgentox.2018.01.003 · Cited by 64 · see citing works
Self-citationThoma, T., Löhr, L., Demuth, P., Hambruch, N., Oesch, F., & Landsiedel, R. (2026) · NAM Journal · doi:10.1016/j.namjnl.2026.100126
- Authors
- Fowler, P., Smith, R., Smith, K., Young, J., Jeffrey, L., Kirkland, D., Pfuhler, S., & Carmichael, P.
- Affiliations
- Unilever (United Kingdom) (GB)
- Covance (United Kingdom) (GB)
- Procter & Gamble (United States) (US)
- Corresponding author
- Fowler, Paul
- Venue
- Mutation Research/Genetic Toxicology and Environmental Mutagenesis
- Publisher
- Elsevier BV
- Published
- 2012-08
- Volume
- 747
- Issue
- 1
- Pages
- 104-117
- ISSN
- 1383-5718 (ISSN-L)
- OpenAlex
- W2064411087
- Cited by
- 83
- References
- 0
- Citations by year
- 2026: 4 · 2025: 2 · 2024: 3 · 2023: 2 · 2022: 2 · 2021: 7 · 2020: 5 · 2019: 7 · 2018: 8 · 2017: 4 · 2016: 7 · 2015: 5 · 2014: 12 · 2013: 11 · 2012: 1
- FWCI
- 2.88
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Mutation Research/Genetic Toxicology and Environmental Mutagenesis (publishedVersion)
- PubMed (publishedVersion)
- Funders
- European Cosmetic Industry Association
- UK National Centre for the 3Rs
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Carcinogens and Genotoxicity Assessment
- Health Sciences › Veterinary › Small Animals › Animal testing and alternatives
- Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Effects of Radiation Exposure
- Keywords
- false positives, in vitro genotoxicity testing, cytogenetic testing, micronucleus induction, toxicity measurement, replication index, CHO cells, TK6 cells, CHL cells, apoptosis and necrosis
- MeSH terms
- Animals, Cell Count, False Positive Reactions, Mammals, Mutagenicity Tests, Micronucleus Tests, Apoptosis
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
