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John M. Gleason, DBA
Creighton University School of Medicine Omaha, Neb

Darold T. Barnum, PhD
University of Illinois Chicago

JAMA. 1992;268(17):2373.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

To the Editor.

—Drs McNagny and Parker¹ report that 39% (160/415) of patients in an inner-city walk-in clinic had cocaine metabolites in their urine. They also report that only 18% (73/415) of their sample were "patients with positive urine assays who admitted to illicit drug use within 1 week" (that is, "admitters"), which suggests that the actual usage rate for cocaine was twice the admitter rate for all drugs (39/18 = 2.17).

In fact, the situation is significantly worse than McNagny and Parker report. The true prevalence of cocaine use is 51%, and thus is almost three times as great as the admitter rate. These higher estimates are the result of adjusting their data for the accuracy of the drug tests, using techniques we recently presented elsewhere.²

McNagny and Parker used unconfirmed positive enzyme-multiplied immunoassay technique (EMIT) assays as the reference standard. They did not check the accuracy of . . . [Full Text PDF of this Article]

Footnotes
Edited by Drummond Rennie, MD, Deputy Editor (West), and Bruce B. Dan, MD, Senior Editor.

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