The utility of drug testing for surveys depends on the type of substance examined as well as on the type of test employed. Multiple tests have more utility than a single test. Drug testing is useful for identifying the levels and sources of under-reporting in a survey and provides a basis for adjusting prevalence estimates based on self-reports.

Hair specimens were collected from 322 subjects and analyzed as part of an experimental study administering household surveys during 1997 to a high-risk community sample of adults from Chicago, Illinois. Toxicologic results were compared with survey responses about recent and lifetime drug use. About 35% of the sample tested positive for cocaine, and 4% tested positive for heroin. Sample prevalence estimates of cocaine use based on toxicologic results were nearly five times the survey-based estimates of past month use and nearly four times the survey-based estimates of past year use. With the hair test results as the standard, cocaine and heroin use were considerably underreported in the survey. Underreporting was more of a problem for cocaine than for heroin. Among those who tested positive, survey disclosure of cocaine use was associated with higher levels of cocaine detected in hair. In general, when recent drug use was reported, it was usually detected in hair. When a drug was detected in hair, use was usually not reported in the survey. When heroin was detected in hair, cocaine was almost always detected as well.

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Since cocaine in blood rapidly hydrolyzes to benzoylecgonine, cocaine concentrations determined in postmortem blood may not reflect the presence or concentration of cocaine in the body at the time of death. The interpretative value of the determination of cocaine and benzoylecgonine in brain tissue was investigated. Cocaine and benzoylecgonine were quantitated by coextraction and formation of the propyl derivative of benzoylecgonine followed by selected ion monitoring gas chromatography/mass spectrometry (GC/MS) using electron ion impact ionization. Cocaine and benzoylecgonine were found to be evenly distributed throughout the brain. Cocaine and benzoylecgonine concentrations were stable in frozen brain tissue (−4°C) on reanalysis after 1 to 3 months of storage, and in refrigerated tissue (10°C) after 30 days of storage. Blood, brain, and liver concentrations of cocaine and benzoylecgonine in 37 cocaine overdose cases and 46 cases in which cocaine was incidental to the cause of death were reviewed. The ratios of cocaine/benzoylecgonine in the toxic cases (brain mean 14.7 and blood mean 0.64) were clearly different from those found in the incidental cases (brain mean 0.87 and blood mean 0.27). The brain/blood ratios of cocaine and benzoylecgonine concentrations generally were characteristic of the time elapsed since cocaine dosing. In cocaine overdose cases, the mean ratio was 9.6 for cocaine and 0.36 for benzoylecgonine. These are within the range found in animal studies for brain/blood ratios of cocaine and benzoylecgonine 0.5 to 2 h after cocaine administration. In incidental cases, the brain/blood ratios were mean 2.5 for cocaine and 1.4 for benzoylecgonine. These ratios confirm the accumulation of benzoylecgonine in brain tissue and its persistence in the body after disappearance of the parent drug.

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