Comparison of three commercial amphetamine immunoassays for detection of methamphetamine, methylenedioxyamphetamine, methylenedioxymethamphetamine, and methylenedioxyethylamphetamine.

Three commercial immunoassays for detection of amphetamines in urine, Abuscreen radioimmunoassay (RIA), enzyme-multiplied immunoassay technique (EMIT), and the TDx fluorescence polarization immunoassay (FPIA), have been investigated for detection of methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxyethylamphetamine (MDE). Blank urine was spiked with 0.1 to 3000 micrograms/mL amphetamine analog and used as sample in the assays. With the RIA and FPIA, MDA displayed a higher cross-reactivity to amphetamine than other analogs, but with EMIT, methamphetamine was relatively similar to amphetamine while MDA, MDMA, and MDE were less reactive. The high specificity RIA and the EMIT confirmation reagents for urine amphetamines produced significant, but relatively minor, reduction in the detectability of these analogs. The variation in cross-reactivity seen between the different assays suggests that RIA, EMIT, and FPIA antibodies have different recognition sites; however, all three immunoassays do detect the illicit amphetamine analogs to varying degrees.