RESUMEN
BACKGROUND: Benzoylecgonine (BE) is the primary urinary metabolite of cocaine. Two enzyme immunoassays were evaluated for the detection of BEin urine with a 300 ng/ml cutoff: the DRI® Cocaine Metabolite Assay and Lin-Zhi International's (LZ) Cocaine Metabolite Enzyme Immunoassay. METHODS: This study involved 1,398 urine specimens from criminal justice and pain management programs. Gas chromatography/mass spectrometry (GC/MS) data were obtained for presumptive positives, and for negative urine specimens yielding responses significantly above the negative control. RESULTS: Approximately 46% (644) of the specimens yielded positive results by DRI, and 47% (664) were positive by LZ. One specimen screened positive with both assays but was found to have a nondetectable BE concentration by GC/MS, indicating one false positive for each assay. Twenty-one specimens yielding negative DRIresults contained BEabove 300 ng/ml, and 29 specimens yielded false negatives with the LZassay. Therefore, the overall agreement between both immunoassays and GC/MSresults was 98%. Assay sensitivity was 0.968 (DRI) and 0.958 (LZ); the selectivity for both assays was 0.999. Urine specimens containing cocaine, additional cocaine metabolites, and other drugs were also tested. No cross-reactivity was observed. CONCLUSION: Both the DRIand LZassays provide a precise, reliable method for the routine detection of BEin urine.