title: Validation of the only commercially available immunoassay for synthetic cathinones in urine: Randox Drugs of Abuse V Biochip Array Technology.
abstract: Deterrence of synthetic cathinone abuse is hampered by the lack of a high-throughput immunoassay screen. The Randox Drugs of Abuse V (DOA-V) Biochip Array Technology contains two synthetic cathinone antibodies: Bath Salt I (BSI) targets mephedrone/methcathinone and Bath Salt II (BSII) targets 3',4'-methylenedioxypyrovalerone (MDPV)/3',4'-methylenedioxy-α-pyrrolidinobutiophenone (MDPBP). We evaluated DOA-V synthetic cathinones performance and conducted a full validation on the original assay with calibrators reconstituted in water, and the new assay with calibrators prepared in lyophilized urine; both utilized the same antibodies and were run on the fully automated Evidence® Analyzer. We screened 20 017 authentic military urine specimens and confirmed positives by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for 28 synthetic cathinones. Limits of detection (LOD) for the original and new assays were 0.35 and 0.18 (BSI), and 8.5 and 9.2 µg/L (BSII), respectively. Linearity was acceptable (R(2)  >0.98); however, a large negative bias was observed with in-house prepared calibrators. Intra-assay imprecision was <20% BSI-II, while inter-assay imprecision was 18-42% BSI and <22% BSII. Precision was acceptable for Randox controls. Cross-reactivities of many additional synthetic cathinones were determined. Authentic drug-free negative urine pH <4 produced false positive results for BSI (6.3 µg/L) and BSII (473 µg/L). Oxidizing agents reduced BSI and increased BSII results. Sensitivity, specificity, and efficiency of 100%, 52.1%, and 53.0% were obtained at manufacturer's proposed cut-offs (BSI 5 µg/L, BSII 30 µg/L). Performance improved if cut-off concentrations increased (BSI 7.5 µg/L, BSII 40 µg/L); however, there were limited confirmed positive specimens. Currently, this is the first and only fully validated immunoassay for preliminary detection of synthetic cathinones in urine. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
authors.affiliation: Chemistry and Drug Metabolism, National Institute on Drug Abuse, NIH, Baltimore, MD, USA; Program in Toxicology, University of Maryland Baltimore, Baltimore, MD, USA.
authors.forename: Kayla N
authors.initials: KN
authors.lastname: Ellefsen
authors.forename: Sébastien
authors.initials: S
authors.lastname: Anizan
authors.forename: Marisol S
authors.initials: MS
authors.lastname: Castaneto
authors.forename: Nathalie A
authors.initials: NA
authors.lastname: Desrosiers
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Martin
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Klette
authors.forename: Marilyn A
authors.initials: MA
authors.lastname: Huestis
mesh_terms: D000470:Alkaloids / Q000652:urine*; D006801:Humans; D013287:Illicit Drugs / Q000652:urine*; D007118:Immunoassay / Q000379:methods*; D057230:Limit of Detection; D008694:Methamphetamine / Q000031:analogs & derivatives / Q000652:urine; D040081:Protein Array Analysis / Q000379:methods; D015813:Substance Abuse Detection / Q000379:methods*
chemical_list: D000470:Alkaloids; D013287:Illicit Drugs; D008694:Methamphetamine; C023665:cathinone; C548233:mephedrone
keywords: MDPV; Randox; immunoassay; mephedrone; synthetic cathinones