Abstract
The usual specimens submitted by a medical examiner for toxicological analysis include blood, urine, bile, vitreous humor, stomach contents, and solid-organ tissue. The detection of drugs in these specimens typically involves a combination of techniques including colorimetry, immunoassay, and gas chromatography. Although many laboratories rely principally on urine for the detection of drugs of abuse by immunoassay, these assays may be applied to other specimen types. An evaluation of Microgenics Corporation's cloned enzyme donor immunoassay (CEDIA) was conducted in order to evaluate its use in the detection of cocaine/cocaine metabolites in vitreous humor specimens. During a 14-month period, 392 vitreous humor specimens were analyzed by the CEDIA DAU Cocaine assay. Instrument parameters were set according to published manufacturer's guidelines. All presumptive positive immunoassay results prompted confirmatory testing and quantitation by gas chromatography-mass spectrometry (GC-MS) of other specimens including blood. Vitreous humor specimens were not tested by GC-MS. Using a approximately 100-ng/mL cutoff, the CEDIA assay produced 23 presumptive positive results, 22 of which were confirmed by GC-MS. The only specimen which could not be confirmed, elicited an immunoassay screen value near the cutoff limit. Routine analysis of blood, urine, bile, and/or bladder wash specimens by gas chromatography-nitrogen phosphorus detection revealed the presence of cocaine/cocaine metabolites in only 7 (31.8%) of the 22 confirmed cases. The concentration ranges of cocaine and benzoylecgonine in the blood specimens were none detected to 337 ng/mL and 17 to 8598 ng/mL, respectively. Cocaethylene was not detected in these cases. Analysis of vitreous humor specimens by CEDIA improved the detection rate of cocaine/cocaine metabolites by 0.7% in the cases submitted to our laboratory during the 14-month period.
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