title: A sensitive assay for urinary cocaine metabolite benzoylecgonine shows more positive results and longer half-lives than those using traditional cut-offs.
abstract: Cocaine is a common drug of abuse. To detect its use, a screening detection concentration for the cocaine metabolite benzoylecgonine is commonly set at 150 ng/mL and its confirmatory cut-off is set at 100 ng/mL. Studies have suggested that these cut-offs may be set too high, allowing some patients with this substance abuse problem to be missed or improperly monitored. With the advent of liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology it is possible to reliably detect and quantify lower concentrations of its metabolite benzoylecgonine as part of a larger drug panel. One purpose of the study was to establish if there was a significant increase in detection of cocaine use with a ten-fold more sensitive cut-off. A very sensitive dilute and shoot assay for benzoylecgonine was developed with a lower limit of quantitation of 5 ng/mL. Validation of the 5 ng/mL cut-off was achieved by plotting all the positive cocaine observations as a frequency distribution on a logarithmic scale. The number of positive results with measurable concentrations below the typical industry 100 ng/mL cut-off level but above the high sensitivity 5 ng/mL cut-off level was observed to be 51.9% of the observed positives. The lower cut-off also allowed a re-evaluation of the window of detection after cessation of use. It was observed to be between 17 and 22 days. © 2016 Precision Diagnostics, LLC. Drug Testing and Analysis published by John Wiley & Sons, Ltd.
authors.affiliation: Precision Diagnostics LLC, Laboratory, 4215 Sorrento Valley Boulevard, San Diego, CA, 92121, USA.
authors.forename: Joyce
authors.initials: J
authors.lastname: Nickley
authors.affiliation: Precision Diagnostics LLC, Laboratory, 4215 Sorrento Valley Boulevard, San Diego, CA, 92121, USA.
authors.forename: Amadeo J
authors.identifier: http://orcid.org/0000-0003-3748-9703
authors.initials: AJ
authors.lastname: Pesce
authors.affiliation: Precision Diagnostics LLC, Laboratory, 4215 Sorrento Valley Boulevard, San Diego, CA, 92121, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Krock
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D003042:Cocaine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine; D019970:Cocaine-Related Disorders / Q000378:metabolism / Q000652:urine*; D006207:Half-Life; D006801:Humans; D057230:Limit of Detection; D015813:Substance Abuse Detection / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: C005618:benzoylecgonine; D003042:Cocaine
keywords: benzoylecgonine; cocaine; half-life; sensitive assay; urine