Evaluation of TDx cocaine metabolite assay

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 metabolite 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.