Combination comet/micronucleus assay validation performed by BioReliance under the JaCVAM initiative

Assessment of the mutagenic potential of para‐chloroaniline and aniline in the liver, spleen, and bone marrow of Big Blue® rats with micronuclei analysis in peripheral blood

“…In challenge to the results of this TGR and parallel micronucleus study, however, are positive results reported in two recent Comet assays conducted with PCA (Barfield and Burlinson, ; Pant and Celestin, – unpublished Arysta LifeScience data, see Supporting Information). In the Barfield and Burlinson study, statistically significant dose‐related increases in the mean and median % tail intensity were observed in the liver and stomach of rats treated with PCA at dose levels of 75 and 150 mg/kg, but not at the low dose of 37.5 mg/kg.…”

Investigation of potential early key events and mode of action for 1,2‐dichloroethane‐induced mammary tumors in female rats

“…In that study, all tissues analyzed were considered positive; however, in contrast to the current OECD guideline recommendations for the Comet assay, DCE was administered by intraperitoneal injection (which is not recommended and is not a relevant route of DCE exposure), only Comet tail length was measured (vs. the required %DNA in tail), only 50 cells were analyzed/animal (vs. the required 150), and only four animals/group (vs. 5) were evaluated. It is worth noting that a structurally related chemical, 1,3‐dichloropropene, was also reported to be positive in all tissues analyzed in the Sasaki et al (1998) publication, but a subsequent study using currently accepted metrics on the same test material indicated a negative response in the stomach and jejunum (even after oral gavage in a point‐of‐contact assessment), indicating that Sasaki et al (1998) study may have been overly sensitive (Pant et al, 2015).…”

Re-analysis results using medians of the data from the JaCVAM-organized international validation study of the in vivo rat alkaline comet assay

“…Data re-analysis was conducted by two types of investigations, i.e., one used each laboratory analysis report [4][5][6][7][8][9][10][11][12][13][14][15][16] and the other was our unified analysis. For both analyses, based on TG 489 [3], the median % tail DNA for each slide was determined, the mean of the 2 median values was calculated for each animal, and then the mean of the individual animal means was determined to give a group mean.…”

“…In laboratory analysis, statistical significance between a negative control group and chemical treatment groups except for the positive control group was analyzed with a one-way analysis of variance (ANOVA) using log-transformed values (3 labs; Lab B: one-sided Simple meanapproach Significant 18 3 3 24 Significant in either statistic 0 5 3 8 Non-significant 2 4 47 53 Number of data 20 12 53 85 Significant: statistically significant in Dunnett's and linear trend test, non-significant: no statistically significant in both statistical analysis methods, significant in either statistic: statistically significant in either but not both of the two statistical analysis methods. and p < 0.03 [4], Lab D: p < 0.05 [6], Lab G: p < 0.001 [9]) followed by a multiple-comparison such as Dunnett's test (3 labs; Lab C: p < 0.05 [5], Lab L: two-sided and p < 0.05 [14], Lab M: two-sided and p < 0.05 [15]), a multiple-comparison with Dunnett's test for nonlog-transformation values (5 labs; Lab E: two-sided and p < 0.05 [7], Lab F: two-sided and p<0.05 [8], Lab I: two-sided and p < 0.05 [11], Lab J: p < 0.05 [12], Lab N: two-sided and p < 0.05 [16]), or a post-hoc right one-sided pairwise comparison using log-transformed values (1 lab; Lab K: one-sided and p < 0.05 [9]). One laboratory (Lab H) did not use statistics because the values in all treatment groups were lower than the respective control values [10].…”

“…Here, we refer to the former method of analysis as the simple mean approach and the latter as the median based approach. Due to TG 489, the individual laboratory reports of the main validation study (Phase 4-2) from most of the participating laboratories were revised and described using their own statistical approach based on using medians (and means) [4][5][6][7][8][9][10][11][12][13][14][15][16]. Also, we separately re-analyzed the Phase 4-2 data based on the median based approach in the same manner as the original statistical analysis of the JaCVAM-organized validation study as reported by Uno et al [2] in order to compare the sensitivity/specificity using the simple mean approach with the median based approach.…”