title: Comparison of fluorescence polarization immunoassay, enzyme immunoassay, and thin-layer chromatography for urine cannabinoid screening. Effects of analyte adsorption and vigorous mixing of specimen on detectability.
abstract: Four commercial assays for the screening of cannabinoids in urine were compared. Urine specimens from 93 selected subjects were run by fluorescence polarization immunoassay on the Abbott TDx; by enzyme multiplied immunoassay with two Syva EMIT assays; and by thin-layer chromatography with the TOXI-LAB system (Marion Laboratories). The TDx cannabinoid threshold can be set anywhere from 25 to 150 micrograms per L. Twenty-five micrograms per L was chosen for this study. The thresholds for EMIT are fixed at 20 micrograms per L for one assay and 100 micrograms per L for the other. The detection limit for TOXI-LAB, according to the manufacturer, can be anywhere from 5 to 50 micrograms/L, depending on the specimen. Urines, positive by at least one method, were further analyzed by gas chromatography with mass spectrometry (GC/MS), The detection limit for the GC/MS method was 10 micrograms per L. The results showed a few false negatives and unconfirmable positives; in general, correlation was considered acceptable. Dose-response curves comparing TDx and EMIT gave paralell results, with comparable cross-reactivity for the major metabolite, 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (delta-9-THC-COOH). A dose-response study of TOXI-LAB using delta-9-THC-COOH also gave acceptable results. Adsorption to glass was investigated using spiked urine; a 27 percent reduction in concentration was caused by this phenomenon. Foaming of spiked urine caused by vigorous mixing resulted in a reversible 89 percent apparent reduction in concentration.
authors.affiliation: Department of Pathology and Laboratory Medicine, Roger Williams General Hospital, Providence, RI 02908.
authors.forename: P
authors.initials: P
authors.lastname: Dextraze
authors.forename: W C
authors.initials: WC
authors.lastname: Griffiths
authors.forename: P
authors.initials: P
authors.lastname: Camara
authors.forename: L
authors.initials: L
authors.lastname: Audette
authors.forename: M
authors.initials: M
authors.lastname: Rosner
mesh_terms: D002186:Cannabinoids / Q000652:urine*; D002855:Chromatography, Thin Layer; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000652:urine; D005454:Fluorescence Polarization; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007124:Immunoenzyme Techniques; D011933:Reagent Kits, Diagnostic
chemical_list: D002186:Cannabinoids; D011933:Reagent Kits, Diagnostic; D013759:Dronabinol