Driving under the influence of drugs--amphetamine concentrations in oral fluid and whole blood samples

This study investigated amphetamine concentrations in both oral fluid and whole blood samples of persons suspected of driving under the influence of drugs. The data for the study were obtained from 153 cases. The mean volume of oral fluid collected with the Intercept oral fluid collection device was 224 microL. Because of the small sample volume of oral fluid, the results of the amphetamine concentrations in oral fluid were not used in the calculations for 39 cases. The total number of cases positive for amphetamine in oral fluid was 100 out of 114. In seven cases the oral fluid sample was positive (cutoff 25 microg/L), even though the whole blood sample was negative (cutoff 20 microg/L). All of the cases found positive in whole blood (n = 93) were also positive in oral fluid. Oral fluid would therefore be well suited as a testing matrix for amphetamine when driving under the influence is suspected. The results nevertheless indicated that the cutoff used for amphetamine in oral fluid (i.e., 25 microg/L) could be higher to correspond to the window of detection given by the level of 20 microg/L in whole blood.