URINE AND SWEAT MONITORING OF ILLICIT COCAINE USE|
Huestis M.A., Preston K.L., Wong C.J., Silverman K., Cone E.J.
National Institute on Drug Abuse, NIH, Addiction Research Center, NIDA, NIH, Baltimore, MD 21224, USA
Sensitive and specific methods for monitoring illicit drug use in clinical treatment and criminal justice populations are needed. A new technique, sweat testing, offers the advantage of monitoring drug use over a period of one week or longer. Sweat patch drug analysis was compared to urine drug testing for the evaluation of cocaine use in methadone maintenance patients in an outpatient setting. The results of urine drug tests (collected thrice weekly and analyzed by EMIT, 300 ng/mL cutoff) from 44 human subjects (N = 1065 specimens) were compared to results of 355 sweat patches that were applied for 7 days over the same period. All sweat patches were analyzed for cocaine by an ELISA immunoassay (cutoff 10 ng/mL). A subset (N = 591) was confirmed by GC/MS (cutoffs = 5 ng/mL for cocaine, benzoylecgonine, and ecgonine methyl ester). If any of three urine specimens collected during the wearing of the sweat patch was positive, drug use was assumed. If all three urine specimens were negative, drug abstinenc was assumed. There was agreement between sweat and urine results for cocaine in 77.7% of the paired specimens. The sensitivity and specificity for detection of cocaine in sweat in comparison to urine were 97.6% and 60.5%. The accuracy, sensitivity and specificity of sweat ELISA cocaine results as compared to sweat GC/MS results were 93.5, 90.5, and 93.1%. Cocaine was detected in 99% of GC/MS positive sweat patches with a mean GC/MS concentration of 989.7 ng/mL. In contrast, the mean benzoylecgonine and ecgonine methyl ester concentrations were 133.5 and 115.9 ng/mL. In 75 cases (21.7%) the sweat was positive for cocaine or metabolites by the ELISA assay, but negative for the three weekly urines at the 300 ng/mL cutoff; however, in 36 of these 75 cases (48%) only one of the two patches applied to the patient was positive. GC/MS analysis of the sweat was available in 43 of these 75 cases and confirmed the presence of cocaine and analytes in 40 or 93% of the samples. Additional controlled drug administraion studies are needed to determine if the increased detection of cocaine by sweat analysis is due to greater sensitivity of sweat testing over urine analysis, or to environmental contamination of the sweat patch. Sweat patch testing may provide an alternative method for monitoring drug use in individuals in drug treatment and criminal justice programs.