10 100 1000 10000 Concentration delta 9-THC in ng/mi
Fig. 5. DrugRead® calibration curve for Drugwipe® Cannabis. The relative intensity of the test line shown is dependent on the concentration of A9-tetrahydrocannabinol.
(positive) saliva samples were tested 10 times. The applied concentrations of drugs were selected in such a way that the cut-off values of Drugwipe were challenged. Three concentration levels of each drug were applied.
The Drugwipe evaluation results are summarized in Table 2.
For each Drugwipe type, the official Drugwipe cut-off level is also given in Table 2. The percentage of correct results represents the proportion of Drug-wipe data that correctly identifies control vs drug-spiked samples. Drug-free and fortified saliva samples with drug concentrations below the official cut-off level of the device were scored as negatives. Saliva samples with drug concentrations above the cut-off level were expected positives. At the time of evaluation, the Drugwipe amphetamines testing device did detected the100-ng/mL concentration with low signal intensity. After this evaluation campaign, the manufacturer of Drugwipe lowered the official cut-off level for amphetamines to 200 |g/mL.
Overall, Drugwipe was 90% accurate in identifying positive saliva samples with drug concentrations above the cut-off levels and 100% accurate in identifying negative saliva samples without or spiked with drug concentrations below the cut-off levels. In this study, Drugwipe was the only instrument-free device that performed according to the specifications and was able to detect THC concentrations at the 50 ng/mL level. The 30 ng/mL level (THC cut-off) was not challenged. THC is the most prevalent drug in the driving population, and a low cut-off for THC is critical for roadside applications.
Independent Evaluation of the Drugwipe® Cut-Off Values With Spiked Saliva Samples
Cut-off value in ng/mL
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