Table 1. Details of curve notation used to classify dose–response data in CPDB.

Group	Definition	Processing required	Number of tumour-tissue data sets a
*	Two or more dose groups showing a linear curve	None	8180
\	Two or more dose groups showing a downward departure from linearity	Only the dose level displaying the highest tumour incidence was retained for TD50 calculation	543
/	Two or more dose groups showing an upward departure from linearity	None	672
Z	Two or more dose groups showing upward or downward departure from linearity	A column in the CPDB data file indicated the number of dose groups used when generating the TD50. The highest tested dose groups were removed until this number of dose groups was reached	1147
0	No dose effect or only a single dose group	Removed from the data set	12 179

^aNumber within the whole data set before the removal of negative authors’ call rows.