Abstract
The performances of four immunoassays (DRI amphetamines, DRI ecstasy, Abuscreen ONLINE amphetamines, and a modified Abuscreen ONLINE amphetamines) were evaluated for control failure rates, sensitivity, and specificity for amphetamine (AMP), methamphetamine (MTH), 3,4-methylenedioxyamphetamine (MDA), and 3,4-methylenedioxymethamphetamine (MDMA). The two DRI reagents and the ONLINE reagents were run according to manufacturer specifications using a Roche Hitachi Modular DDP system. The modified ONLINE reagent was calibrated with MDMA and had 16mM sodium periodate added to the R2 reagent. These assays were run on approximately 27,500 human urine samples and 7000 control urine samples prepared at 350 and 674 ng/mL over the course of 8 days. All assays were calibrated using a single point, qualitative cutoff standard with the manufacturer-recommended compound at the Department of Defense cutoff (500 ng/mL). Gas chromatography-mass spectrometry (GC-MS) confirmation was conducted on screened-positive samples. Control performance for the manufacturer recommended assays was excellent, with a maximum qualitative control failure rate of 2.03%. The modified ONLINE reagent demonstrated poor control performance with a maximum failure rate of 38.3% and showed no improved MDMA sensitivity when compared with the ONLINE reagent; the confirmation rate (20%) was improved when compared with the production ONLINE reagent (8%). The DRI ecstasy reagent provided improved sensitivity for MDMA as compared with the ONLINE reagent, with approximately 23% more samples screening and confirming positive for MDMA and a confirmation rate of approximately 90%. The DRI methamphetamine reagent had a low confirmation rate (6% or less) and produced numerous positives for samples with only ephedrine or pseudoephedrine present.
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