Immunoassay Screening of Lysergic Acid Diethylamide (LSD) and its Confirmation by HPLC and Fluorescence Detection Following LSD ImmunElute Extraction

Of 3872 urine specimens screened for LSD with the CEDIA DAU assay, 48 were initially positive, but only 13 (27%) were confirmed by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) after immunoaffinity extraction. The DPC Coat-a-Count RIA showed complete agreement with HPLC-FLD at concentrations below 500 pg/mL. Fifteen compounds—including ambroxol, diphenhydramine, amitriptyline, and lidocaine—were identified as causing false positives in the CEDIA assay. The IAE/HPLC-FLD method is rapid, reliable, and cost-effective for infrequent LSD analysis, and its chromatographic detection of LSD, nor-LSD, and iso-LSD is unaffected by these cross-reacting compounds even at 100 ng/mL.

Study at a glance

Abstract

In all, 3872 urine specimens were screened for lysergic acid diethylamide (LSD) using the CEDIA DAU LSD assay. Forty-eight samples, mainly from psychiatric patients or drug abusers, were found to be LSD positive, but only 13 (27%) of these could be confirmed by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) following immunoaffinity extraction (IAE). Additional analysis for LSD using the DPC Coat-a-Count RIA was performed to compare the two immunoassay screening methods. Complete agreement between the DPC RIA assay and HPLC-FLD results was observed at concentrations below a cutoff concentration of 500 pg/mL. Samples that were LSD positive in the CEDIA DAU assay but not confirmed by HPLC-FLD were also investigated for interfering compounds using REMEDI HS drug-profiling system. REMEDI HS analysis identified 15 compounds (parent drugs and metabolites) that are believed to cross-react in the CEDIA DAU LSD assay: ambroxol, prilocaine, pipamperone, diphenhydramine, metoclopramide, amitriptyline, doxepine, atracurium, bupivacaine, doxylamine, lidocaine, mepivacaine, promethazine, ranitidine, and tramadole. The IAE/HPLC-FLD combination is rapid, easy to perform and reliable. It can reduce costs when standard, rather than more advanced, HPLC equipment is used, especially for labs that perform analyses for LSD infrequently. The chromatographic analysis of LSD, nor-LSD, and iso-LSD is not influenced by any of the tested cross-reacting compounds even at a concentration of 100 ng/mL.