Comparison of eight commercial on-site screening devices for drugs-of-abuse testing

Eight commercially available on-site drugs-of-abuse testing devices for detecting cannabinoids (THC-COOH), opiates (OPI), cocaine (COC), amphetamines (AMP), metamphetamines (MET) and benzodiazepines (BZO) were evaluated. The used urine specimens suspected of being drug positive were all confirmed by gas chromatographic/mass spectrometry (GC/MS). For AMP and MET, sensitivities varied between 83 and 95% and specificities between 98 and 100%. Correspondingly, sensitivities between 88 and 98% and specificities between 95 and 100% were observed for THC-COOH. For BZO, sensitivities varied between 91 and 97% and specificities between 97 and 100%. Only a few confirmed positive samples were available for OPI and COC, the sensitivities being between 83 and 100% and 100%, respectively. On-site devices did not always find extremely high drug concentrations. False-negative results were found with AMP in particular. Pholcodine, commonly used as medicine, was observed to give false-positive results with most of the devices and was not, however, included in given cross-reactivity tables. It was found that the devices differed markedly with respect to interpretation of test results and to ease of test performance, leading to the suggestion that different criteria for selecting on-site devices for either emergency laboratories in hospitals or for police stations and prisons should be used. Since the overall specificity of any of the devices was not 100% and false positives were identified, we found it important to confirm any positive screening test result.