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Abstract
The percent active (A) and inactive (I) chemicals in a database can directly affect the sensitivity (% active chemicals predicted correctly) and specificity (% inactive chemicals predicted correctly) of structure–activity relationship (SAR) analyses. Subdividing the National Center for Toxicological Research (NCTR) liver cancer database (NCTRlcdb) into various A/I ratios, which varied from 0.2 to 5.5, resulted in sensitivity/specificity ratios that varied from 0.1 to 6.5. As percent active chemicals increased (increasing A/I ratio), the sensitivity rose, the specificity decreased, and the concordance (% total chemicals predicted correctly) remained fairly constant. The numbers of chemicals in the various data sets ranged from 187 to 999 and appeared to have no affect on any of the 3 predictors of sensitivity, specificity, or concordance.
Notes
a All chemicals that were classified by the NTP designation of associated (a), probable (p), equivocal (e), or inadequate (i) were removed from the data set, as were all cancer-other classification (inactive classification in this database).
a All chemicals that were classified by the NTP designation of associated (a), probable (p), equivocal (e), or inadequate (i) were removed from the data set, as were all cancer-other classification (inactive classification in this database).