An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments |
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Authors: | Helle Sørensen Nina Cedergreen Ib M Skovgaard Jens C Streibig |
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Institution: | 1.Department of Natural Sciences,University of Copenhagen (LIFE),Frederiksberg C,Denmark;2.Department of Agricultural Sciences,University of Copenhagen (LIFE),Taastrup,Denmark;3.Department of Agricultural Sciences,University of Copenhagen (LIFE),Frederiksberg C,Denmark |
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Abstract: | Synergism and antagonism are often defined in relation to the model of Concentration Addition (CA). Hence, it is vital for
the conclusion of mixture toxicity studies to be able to test whether an observed deviation from CA reflects a true deviation
or whether it is simply due to random variation. In this paper we consider a non-linear regression model for the classical
ray designs for binary mixture experiments. The model combines dose–response curves for each mixture in the experiment with
an isobole model, describing possible deviations from CA. The method allows us to test whether the chosen isobole model is
reasonable for the data and to test the hypothesis of CA. Furthermore, it provides us with a measure of the degree of synergism/antagonism.
The method is flexible since both the dose–response relationships and the isobole model can be chosen arbitrarily. We demonstrate
the use of the method on datasets where combinations of pesticides are tested on a floating plant, Lemna minor, and an algae, Pseudokirchneriella subcapitata. Furthermore, we conduct a simulation study in order to explore the power with which a specific deviation from CA can be
distinguished in different test-systems. |
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Keywords: | Concentration addition Dose– response curves |
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