Comparison of EMIT(R) II, CEDIA(R) and DPC(R) RIA Assays for the Detection of Lysergic Acid Diethylamide in Forensic Urine Samples

Abstract

In an effort to determine a practical, efficient, and economical alternative for the use of a radioimmunoassay (RIA) for the detection of lysergic acid diethylamide (LSD) in human urine, the performance of two photometric immunoassays (Dade Behring EMIT II and Microgenics CEDIA) and the Diagnostics Products Corp. (DPC) RIA were compared. Precision, accuracy, and linearity of the 3 assays were determined by testing 60 replicates (10 for RIA) at 5 different concentrations below and above the 500-pg/mL LSD cut-off. The CEDIA and RIA exhibited better accuracy and precision than the EMIT II immunoassay. In contrast, the EMIT II and CEDIA demonstrated superior linearity r2 = 0.9809 and 0.9540, respectively, as compared with the RIA (r2 = 0.9062). The specificity of the three assays was assessed using compounds that have structural and chemical properties similar to LSD, common over-the-counter products, prescription drugs and some of their metabolites, and other drugs of abuse. Of the 144 compounds studied, the EMIT II cross-reacted with twice as many compounds as did the CEDIA and RIA. Specificity was also assessed in 221 forensic human urine specimens that previously screened positive for LSD by the EMIT II assay. Of these, only 11 tested positive by CEDIA, and 3 were positive by RIA. This indicated a comparable specificity performance between CEDIA and RIA. This also was consistent with a previously reported high false-positive rate of EMIT II (low specificity). Each of the immunoassays correctly identified LSD in 23 out of 24 human urine specimens that had previously been found to contain LSD by gas chromatography-mass spectrometry at a cut-off concentration of 200 pg/mL. The CEDIA exhibited superior precision, accuracy, and decreased cross-reactivity to compounds other than LSD as compared with the EMIT II assay and does not necessitate the handling of radioactive materials.

Analysis of Ergot Alkaloids

“…Immunoaffinity based extraction and clean-up methods have been applied to LSD to produce samples suitable for determination by GC-MS or LC-MS and some extraction devices are now available commercially [ 68 , 69 , 70 ].…”

What Can a Urine Drug Screening Immunoassay Really Tell Us?

“…The immunoassay for LSD is inherently susceptible to inappropriately positive results due to the fact that LSD is extensively metabolized and only a very small fraction of the parent molecule appears in urine. 99 This translates to an immunoassay with high sensitivity, but low specificity. Newer generation LSD immunoassays are designed to target the primary metabolite 2-oxo-3-hydroxy-LSD, which may improve detectability as it achieves higher and more detectable concentrations in the urine.…”

Forensic Science

“…The importance of vacutainer selection in forensic toxicological analysis of drugs of abuse was studied using FPIA immunoassays and GC/MS (412). The analysis of urine for LSD has been done by micellar electrokinetic chromatography (413), immunoassays (414), HPLC with fluorescence detection (415), and LC/MS (416). The analysis of psilocyn and psilocybin in developmental mushrooms has been described (417).…”