Semi-quantitative analysis of drugs of abuse in human urine by end-point dilution flow immunochromatographic assay
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IGINAL RESEARCH PAPER
Semi-quantitative analysis of drugs of abuse in human urine by end-point dilution flow immunochromatographic assay Sayed M. Badawy 1 Received: 21 February 2020 / Accepted: 6 July 2020 # Akadémiai Kiadó, Budapest, Hungary 2020
Abstract A novel flow chromatographic immunoassay method using end-point dilution was developed in our laboratory as an alternative to the homogeneous enzyme immunoassay, for low-cost, simple, and fast semi-quantitative analyses of drugs of abuse in human urine. A serial dilution of the positive test sample using rapid test cassettes is continued until reaching the lowest dilution, with a visual detectable colored band at the definite cutoff concentration. The calibration curve of the equivalent dilution volume (end-point titers) vs concentration of the spiked urine sample exhibited excellent linearity with a coefficient of determination R2 of 0.9995 for cannabinoids and 0.9997 for opiates; this indicates that end-point dilution flow chromatographic immunoassay can be used in a semiquantitative mode for drugs of abuse urine analysis. The developed dilution method exhibits a visual limit of detection (LOD) at the cutoff, and a linear relationship ≥ 50 ng/mL for cannabinoids and ≥ 300 ng/mL for opiates, without an upper limit of detection. The recovery of spiked urine samples is within 98–111% of theoretical values for cannabinoids and 101–110% for opiates. Good correlation was obtained between end-point dilution flow chromatographic immunoassays and homogenous immunoassays with a Thermo Scientific Indiko autoanalyzer for cannabis abuse specimens. Keywords Semi-quantitative . Drugs of abuse . End-point dilution . Flow immunochromatographic assay
1 Introduction Substance abuse has become a public health concern in Egypt. Tramadol, cannabis, and heroin are the most popular drugs of abuse (DOA), particularly among the youth, while hashish and opium have been used for centuries. It is estimated that the drug addiction rate in Egypt is twice the global rates, with approximately more than 9 million people using narcotics, which is double the international average. The use of narcotics in Egypt began to reach serious levels in the 1980s. It is reported that Egyptian addicts spend about $3.0 billion on drugs annually. The number of heroin addicts was estimated between 20,000 and 30,000 in 2005. In 2012, the United Nations Office on Drugs and Crime (UNODC) reported that 6–8% of Egypt’s population aged 15–64 used cannabis [1–7]; * Sayed M. Badawy [email protected] 1
National Center for Clinical and Environmental Toxicology, NECTR, Faculty of Medicine, Cairo University, Giza, Egypt
the government rolled out a drug test procedure for state employees after multiple disastrous transport accidents [2]. There is an urgent need for a rapid and accurate method for quantitative on-site detection of DOA. Gas chromatography– mass spectrometry (GC–MS) and liquid chromatography– tandem mass spectrometry (LC–MS/MS) techniques are not appropriate for quick analyses of numerous specimens as
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