|SOFT - TIAFT 1998||Poster Session 1||Wednesday October 7, 1998|
EVALUATION OF A ON-SITE METHOD FOR THE DETECTION OF DRUGS OF ABUSE IN SALIVA|
Clare Malcolm, John S. Oliver, Chris W. Hand* and Dene Baldwin*
Department of Forensic Medicine and Science, University of Glasgow, University Place, Glasgow, G12 8QQ, UK
Detection of drugs of abuse in saliva offers a convenient, non-invasive, method in place of or to complement conventional urine drug screening. A total of 72 saliva samples were volunteered by patients participating in a drug rehabilitation programme using the Salivette® and swabs. Saliva samples are difficult to adulterate and samples containing visible blood were discarded. The saliva samples were analysed using of the COZART Rapiscan test system and screened for drugs of abuse using the laboratory-based method of microplate enzyme-immunoassay. Confirmational analysis was then carried out using solid-phase extraction followed by gas chromatography/mass spectrometry (31 cases for methadone and 24 cases for opiates) or high performance liquid chromatography (20 cases for benzodiazepines).
A swab was used to collect saliva from the subject. The swab was then inserted into a test cartridge housing the immunoassay. The test cartridge is designed to allow multiple drugs to be tested from a single specimen. This disposable testing cartridge was then inserted into the instrument for analysis. The COZART Rapiscan is a hand-held instrument which analyses, interprets and displays results of the test. Investigations of benzodiazepines, opiates, cannabinoids, amphetamines and cocaine metabolites were carried out with results for all drug groups displayed after five minutes. The instruments are factory set to give positive or negative results relative to a cut-off level but as part of this study these were qualitatively set.
All methods were able to detect the low levels of drugs present in saliva. The Rapiscan device was able to detect less than 1 ng/mL for the drugs tested. The Rapiscan response was linear for all drugs analysed. For methadone the calibration curve was linear over the concentration range of 0-250 ng/mL, r2 = 0.997, with a CV of < 2.25% for each concentration measured (n = 7).
Spiked and case samples were analysed by the Rapiscan, by microplate and by GC/MS or HPLC. A linear response ( r2 = 0.947) was obtained when comparing the results of the Rapiscan with those by GC/MS for methadone (n = 17). Seven cases were positive for methadone by GC/MS (mean concentration = 0.40 ug/mL, range 0.15-0.73 ug/mL) with a corresponding Rapiscan response (mean = -399, range -167 to -733). The additional ten cases which were negative by GC/MS for methadone, were also negative by the Rapiscan and enzyme immunoassay. The results correlated well for all methods and drugs analyzed. Similar agreement was obtained with patient specimens for opiates and benzodiazepines.