On-site testing of saliva and sweat with Drugwipe and determination of concentrations of drugs of abuse in saliva, plasma and urine of suspected users.
Potential drug users participated voluntarily in a Belgian study on the usefulness of the non-instrumental immunoassay Drugwipe (Securetec, Germany) for the screening of cocaine, opiates, amphetamine and cannabinoids in saliva and sweat. If one of the screening assays (urine, oral fluid, sweat) showed a positive result, blood and saliva were collected. The on-site Drugwipe results were correlated with the Drugwipe results for saliva in the laboratory and with the GC/MS results of the corresponding saliva, plasma and urine samples and pharmacological effects at the time of sampling. The Drugwipe assay proved to be sufficiently sensitive for the detection of recent cocaine (n = 6) and amphetamine (n = 15) abuse, whether the device was wiped on the tongue or on the surface of the body, or when a saliva sample was applied to the wiping part. In five of the six potential cocaine users, the saliva concentrations of cocaine exceeded 1,000 ng/ml. In the amphetamine group, the saliva concentrations of amphetamine, MDMA or both were high (> 1,000 ng/ml) in 13 subjects. For cocaine and amphetamine, the positive scores for Drugwipe matched the GC/MS results for the three body fluids. Recent heroin abuse (n = 5) could be demonstrated to some extent with Drugwipe on samples from the tongue but only the two subjects with the highest saliva concentrations of MAM (> 500 ng/ml) and morphine (> 500 ng/ml) were positive. If the legal cut-off value for driving under the influence of opiates in Belgium (20 ng/ml of free morphine in plasma) was taken into account, only three subjects would have been legally positive. For cannabinoids (n = 15), false negatives and even some false positives were observed. Saliva can be considered as a useful analytical matrix for the detection of drugs of abuse after recent abuse when analysed with GC/MS.