Urine Screening for Narcotics under Court-Imposed Abstinence Requirements: Comparative Validity of Forensic-Toxicological Analyses with Involvement of Public Health Services

Abstract

Assessment of the comparative validity between qualitative and quantitative analyses of urine screenings for defined narcotics residues under court-imposed abstinence restrictions. Following the introduction of a valid marker system which, based on the application of a defined sugar substance and its detection in the urine of person under probation in 2006, urine samples were assayed in administrative cooperation by a Bavarian public health office for probationary services for evidence of narcotics. The urine samples were sent to an external laboratory in order to carry out forensic toxicological analyses for defined narcotics. The qualitative and quantitative laboratory results were reported back to the public health department so that a digital-based data set of a total of 380 persons with more than 27,000 individual analyses from a total of 14 consecutive calendar years could be established and retrospectively evaluated in an anonymised form. The overall prevalences of findings positive for narcotics were 2.7% (n=366 of 13,531) for the qualitative and 2.6% (n=348 of 13,525) for the subsequent quantitative result categorisations, with cannabis and opiates being detected most frequently in both test methods. Using the kappa coefficient as a quantitative measure for the comparative validity of both test methods, the test results showed the highest agreement (1.000) for buprenorphine and lowest agreement for PCP (0.880). No age- and gender-specific stratifications could be recorded for a total of ten different narcotic substances; substance-specific case numbers differed among the analyses. Based on the strong to very strong correspondences between qualitative and quantitative narcotics analysis results, it could be assumed that both analysis methods accurately recorded violations of abstinence requirements and were to be classified as sufficiently substantiating for judicial decisions under the Narcotics Act (Betäubungsmittelgesetz, BtMG). According to these results, the content of urine screenings for narcotics controlling abstinence should be discussed.