Since the collection and analysis of drugs in oral fluid (OF) at the roadside has become more feasible with the introduction of portable testing devices such as the Alere DDS2 Mobile Test System (DDS2), the current study compared the on-site results for the DDS2 to laboratory-based confirmatory assays regarding the detection of drugs of abuse in human subjects.
As part of a larger Institutional Review Board approved study, two OF samples were collected from each participant at a music festival in Miami, FL, USA. One OF sample was field screened using the DDS2, and a confirmatory OF sample was collected using the Quantisal OF collection device and submitted to the laboratory for testing. In total, 124 subjects participated in this study, providing two contemporaneous OF samples. DDS2 field screening yielded positive results for delta-9-tetrahydrocannabinol (THC) (n = 27), cocaine (n = 12), amphetamine (n = 3), methamphetamine (n = 3) and benzodiazepine (n = 1). No opiate-positive OF samples were detected. For cocaine, amphetamine, methamphetamine and benzodiazepines, the DDS2 displayed sensitivity, specificity and accuracy of 100 percent. For THC, the DDS2 displayed sensitivity of 90 percent, specificity of 100 percent, and accuracy of 97.5 percent, when the threshold for confirmation matched that of the manufacturers advertised cut-off. When this confirmatory threshold was lowered to the analytical limit of detection (i.e., 1 ng/mL), apparent device performance for THC was poorer due to additional samples testing positive by confirmatory assay that had tested negative on the DDS2, demonstrating a need for correlation between manufacturer cut-off and analytical reporting limit. These results from drug-using subjects demonstrate the value of field-based OF testing, and illustrate the significance of selecting an appropriate confirmation cut-off concentration with respect to performance evaluation and detection of drug use. (publisher abstract modified)