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An investigation of new toxicity test method performance in validation studies: 3. sensitivity and specificity are not independent of prevalence or distribution of toxicity

Gillette Environment, Health & Safety, Needham, Massachusetts, USA; leon_bruner{at}gillette.com

G J Carr

The Procter & Gamble Company, Miami Valley Laboratories, Cincinnati, Ohio, USA

J W Harbell

R D Curren

Institute for In Vitro Sciences, Gaithersburg, Maryland, USA

Often, the only measures of toxicity test performance provided in validation studies are the contingent probability statistics (CPS) sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Sensitivity and specificity are generally used in preference to NPV and PPV since NPV and PPV are assumed to vary with changes in prevalence while sensitivity and specificity are assumed to be independent of changes in prevalence. The purpose of the studies reported here was to test whether or not sensitivity and specificity are actually independent of changes in prevalence. Results derived from these studies indicate that sensitivity and specificity vary significantly depending on the prevalence of toxic substances in the set of chemicals being tested. This means sensitivity and specificity should not always be considered constant indicators of toxicity test performance.

Key Words: correlation • negative predictive value • positive predictive value • prediction interval • prevalence • sensitivity • specificity • toxicity test performance measurement • toxicity test validation • validation

Human & Experimental Toxicology, Vol. 21, No. 6, 325-334 (2002)
DOI: 10.1191/0960327102ht254oa


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