Clinical Chemistry
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Clinical Chemistry 43: 100-103, 1997;
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(Clinical Chemistry. 1997;43:100-103.)
© 1997 American Association for Clinical Chemistry, Inc.

Articles

Lowering cutoffs for initial and confirmation testing for cocaine and marijuana: large-scale study of effects on the rates of drug-positive results

William E. Wingert
A large-scale study was conducted to determine whether lowering the initial testing and confirmation testing cutoffs in urine would significantly affect the positive rates for cocaine (COC) and marijuana (THC). Customary cutoffs for COC are 300 µg/L and 150 µg/L for initial testing (screening) and gas chromatography–mass spectrometry (GC-MS; confirmation), respectively; for THC, the usual respective cutoffs are 50 µg/L and 10 µg/L. By applying a screening cutoff of 100 µg/L for COC and lowering the GC-MS cutoff to 50 µg/L, the COC-positive rate increased from 1.2% to 2.1%. For THC, lowering the screening cutoff to 20 µg/L while leaving the GC-MS cutoff at 10 µg/L increased the THC-positive rate from 2.8% to 4.1%. These increases appear noteworthy.


Key Words: indexing terms: abused drugs • screening • gas chromatography–mass spectrometry • urine




The following articles in journals at HighWire Press have cited this article:


Home page
 Clin. Chem.Home page
V. I. Luzzi, A. N. Saunders, J. W. Koenig, J. Turk, S. F. Lo, U. C. Garg, and D. J. Dietzen
Analytic Performance of Immunoassays for Drugs of Abuse Below Established Cutoff Values
Clin. Chem., April 1, 2004; 50(4): 717 - 722.
[Abstract] [Full Text] [PDF]


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