AN EFFICIENT EXPERIMENTAL-DESIGN FOR DETECTING DEPARTURE FROM ADDITIVITY IN MIXTURES OF MANY CHEMICALS

Berenbaum (J. Theor. Biol. 114 (1985) 413-431) described a procedure f or detecting and characterizing departure from additivity in a combina tion of c (c greater than or equal to 2) chemicals. The attraction of this approach is that it is based on the concentration-response relati onship of each of the individual components and, under the assumption of additivity, it is straight forward to predict the response of a giv en combination. Deviations between the observed and predicted response s for the combination are associated with departures from additivity. Berenbaum based his conclusions regarding synergism/antagonism on nume rical differences which do not take into account inherent biological v ariability. We have developed a procedure which incorporates experimen tal variation is based on each individual component's concentration-re sponse relationship, and leads to a conclusion regarding the statistic al significance of any departure from additivity. The procedure is ill ustrated with an example.