Use of the USDT flow immunosensor for quantitation of benzoylecgonine in urine

The flow immunosensor works on a principle somewhat distinct from other immunoassay systems in that it performs a displacement immunoassay. Antibody-coated matrices are saturated with fluorescently labeled benzoylecgonine (BE), which is released and measured in the presence of BE-containing urine and measured downstream from the matrix. The same antibody matrix can be used for many samples. A flow immunosensor instrument, built by US Drug Testing, Inc., has recently received ‘Premarket Notification’ (510(K)) from the Food and Drug Administration (FDA) to screen urine for the presence of the cocaine metabolite BE. The performance of the flow immunosensor for screening BE in urine was validated by comparison with results of a blind study using the Syva EMIT, the Abbott TDx and gas chromatography-mass spectroscopy (GC-MS). Potentially interfering drugs were also spiked into urine and evaluated using the flow immunosensor. While the FDA approval is for determining whether the BE concentration is above or below the 300 μg/l cutoff recommended by the National Institute of Drug Abuse, we have also shown that the flow immunosensor can be adapted to produce quantitative determinations of the amount of BE in the urine samples. The reliability of the quantitation was confirmed by testing 100 urine samples containing unknown amounts of BE using the flow immunosensor, GC-MS and the Abbott TDx system. Comparison of quantitative data obtained using the immunosensor and GC-MS showed a 97% correlation, compared with a much lower value for data from the TDx and GC-MS.