SETAC Presentation: Comparison of Xenopus laevis NF developmental stage-matched control data in Amph
SETAC Presentation: Comparison of Xenopus laevis NF developmental stage-matched control data in Amphibian Metamorphosis Assay continuous quantitative endpoints (HLL, SVL, wet weight)
The analysis of continuous quantitative Xenopus laevis endpoints such as snout-to-vent length (SVL), hind limb length (HLL), nHLL (normalized by SVL) and wet weight is performed to assess statistically significant differences between the negative control and active substance treatments in the Amphibian Metamorphosis Assay (AMA) for the detection of potential thyroid modes of action according to Guidelines OECD 231 and OPPTS 890.1100. However, the current statistical analysis of these parameters at Day 7 and 21 is routinely performed by using the replicate means or medians of the recorded HLL, nHLL, SVL and wet weight individual values without taking into consideration the different stages of development within each control or treatment replicate. Furthermore, these endpoints are well known to be directly impacted by developmental stage in tadpoles and so using stage-matched data may have an impact in the interpretation of the biological results. This is also the case for tadpole thyroid gland histopathological findings, where it is already recognised in both Guidelines that the most appropriate approach is to use NF developmental stage-matched tadpoles for evaluation. Consequently, individual control HLL, nHLL, SVL and wet weight values on Day 7 and 21 from the available data set have been extracted and evaluated according to NF developmental stage. The analysis presented here aims to develop a NF developmental stage-matched Historical Control Database (HCD) that allows the assessment of potential impact in the outcome of statistically significant results of these thyroid screening parameters, as well as the variability of NF developmental stage-matched control data across different GLP AMA-performing laboratories.