Indirect enzyme-linked immunosorbent assay for the quantitative estimation of lysergic acid diethylamide in urine.

A new antibody to lysergic acid diethylamide (LSD) was used to develop a novel indirect ELISA for the quantification of drug in urine. Evaluation of the new assay with the commercially available LSD ELISA (STC Diagnostics) shows improved performance. The test requires 50 microL of urine, which is used to measure concentrations of drug in the microg/L to ng/L range. The limit of detection was 8 ng/L compared with 85 ng/L in the commercial assay, and analytical recoveries were 98-106%. Our test detected 0.1 microg/L of LSD in urine with an intraassay CV of 2.4% (n = 8) compared with 6.0% for a 0.5 microg/L sample in the commercial assay (n = 20). The upper and lower limits of quantification were estimated to be 7 microg/L and 50 ng/L, respectively. Specificity was evaluated by measuring the extent of cross-reactivity with 24 related substances. Drug determination using the new assay offers both improved sensitivity and precision compared with existing methods, thus facilitating the preliminary quantitative estimation of LSD in urine at lower concentrations with a greater degree of certainty.