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samples indicated that 58 were positive. Of the 34 negatives indicated by Drug-wipe, 31 were confirmed negatives by blood analysis. Table 4 shows a breakdown of the data for the three drugs tested. Because blood was the only reference specimen, Drugwipe results were grouped into confirmed or unconfirmed positives and negatives. Overall accuracy was 93%, diagnostic sensitivity 95%, and specificity 89%. The positive predictive value is 94%. Discrepancies between Drugwipe results and the results of the blood analysis could be a result of differential pharmacological distribution of drugs in sweat and blood. During the first 30 to 90 min, there is a diagnostic window in which drug concentrations present on the skin are not yet above the cut-off values detectable by Drugwipe. In general, the concentration curve for drugs in sweat tends to shift towards a longer time window indicating a longer distribution period. The findings of this field trial, together with previous laboratory studies under controlled conditions, clearly confirm the usefulness of Drugwipe as a sweat test for roadside operations.

As a result of this field trial, the majority of the German states have since introduced Drugwipe as a sweat test for routine roadside screening for DUID. Sweat testing is favored over that of saliva because it is less invasive and more hygienic, and can even be performed without cooperation of the driver suspects. Table 5 summarizes the overall data of a 6-mo field operation in Nordrhein-Westfahlen (8) starting in the summer of 2003. Of 1763 tests, accuracy and predictive values of Drugwipe ranged between 93 and 97%. In this operation, field officers were extensively trained in impairment recognition as well as general metabolic patterns of different drugs in different human testing specimens. Through this training, the police officers developed a thorough understanding of the advantages and disadvantages of various body fluids for roadside testing and the importance of their observations during the testing process.

Table 5

Overall Accuracy and Positive Predictive Values for Drugwipe® Under Field Conditions

Table 5

Overall Accuracy and Positive Predictive Values for Drugwipe® Under Field Conditions

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