Evaluation of TDx Cocaine Metabolite Assay

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Abstract
The TDx cocaine metabolite fluorescence polarization immunoassay (Abbott Laboratories) for the detection of benzoylecgonine (BE) in urine was evaluated. The threshold concentration for BE detection was 0.3 mg/L. The within-and between-run precision of the assay gave coefficients of variation less than 2.3% and 3.5%, respectively. One hundred twenty clinic urines positive for BE by high-pressure liquid chromatography (HPLC) were analyzed by the TDx and EMIT-dau cocaine metabollte assays. All three methods were positive for BE in 116 samples, 96.7%. Two samples were positive by TDx and negative by EMIT-dau, and two samples were positive by EMIT-dau and negative by TDx. Cocaine and ecgonine methyl ester cross reactivity with the TDx assay was less than 2%. One hundred drugs and drug metabolites were added to drug-free urine resulting in no false positive reactions. The same drugs and drug metabolites were also added to urine with 3.0 mg/L BE and analyzed by the TDx. No false positive reactions or inhibition of BE detection occurred.