Validity Testing of the EZ-SCREEN(R) Cannabinoid Test

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Abstract
Recently, a number of “quick tests” became available for use in on-site drug testing. These tests offer advantages in simplicity, ease of performance, and rapid access to test results. However, there is a paucity of data on the validity of these tests for the detection of drugs of abuse. This report describes a validity study of the EZ-SCREEN® cannabinoid test for the detection of cannabinoids in urine. Three healthy, male volunteers with a history of marijuana use participated in the study. Each subject smoked 1, 2, or 4 marijuana cigarettes (2.6% THC) on each test day. Urine samples were collected and incorporated into a specimen set consisting of 178 clinical urine samples, 72 urine samples containing known amounts of drug, and 50 drug-free urine samples. The specimen set was randomized and analyzed under blind conditions by the EZ-SCREEN test and by GC/MS for 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH). Results were interpreted independently by three readers. Concordance analysis was performed by comparison of results of the EZ-SCREEN test with GC/MS. The EZ-SCREEN test was highly sensitive and produced positive results at a standard THCCOOH concentration of 5 ng/mL. While showing high sensitivity to THCCOOH, the assay demonstrated low cross-reactivity with Δ9-tetrahydrocannabinol (THC) and other cannabinoids. No false-positive results were recorded with 50 drug-free urine samples, but one reader recorded eight undecided results. Overall agreement between the three readers for the EZ-Screen results was approximately 80%. Delayed readings and photocopy readings tended to be less accurate than readings obtained at 3 min. Overall, the EZ-SCREEN test was easy to perform and provided rapid turnaround of results. Because the assay appears to be highly sensitive to THCCOOH in urine, positive results may not be confirmed by GC/MS at a cutoff of 15 ng/mL.

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