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Discrepant
analysis: a biased and an unscientific method for estimating test sensitivity
and specificity.
Journal of Clinical Epidemiology 2001;52(12):1231-1237.
Hadgu A.
Abstract
Discrepant analysis is a widely used technique for estimating test performance
indices (sensitivity, specificity, etc.) of DNA-amplification tests for
detecting infectious diseases. It has recently been claimed that the
discrepant analysis-based estimates of specificity are typically less
biased than those based on culture and that the discrepant analysis-based
specificity shows little appreciable bias. In this article, I show that
those conclusions are incorrect. Using a typical example from the published
literature, I show that the discrepant analysis-based estimates of sensitivity
and specificity can generate a significant and clinically important overestimation
of the true sensitivity and specificity values. Moreover, I demonstrate
that the concept of discrepant analysis is profoundly flawed and unscientific.
It violates a fundamental principle of diagnostic testing-the principle
that the new test should not be used to determine the true disease status.
Thus, the major problem with discrepant analysis is not only that it
is biased but that it is unscientific. Therefore, discrepant analysis
should not be adopted for the evaluation of any diagnostic or screening
test.