Drugs of abuse testing by tandem mass spectrometry: a rapid, simple method to replace immunoassays.

ABSTRACT

PRIMARY OBJECTIVE: To replace immunoassay screening for drugs of abuse (DOA) with a cost-effective tandem mass spectrometry method. SECONDARY OBJECTIVE: To substantially expand the drugs of abuse assay menu. DESIGN AND METHODS: The requirement was to perform high throughput DOA screening for 200 urine specimens/day for 40 drugs/metabolites. The total analysis time had to be <5 min. We used UPLC chromatography, small particle size LC columns and fast scanning tandem mass spectrometry. Urine samples were hydrolyzed enzymatically, diluted and injected with isotopically labeled internal standards. The data produced was transferred by exporting reports as text files to a LIMS system followed by auto certification of the results. RESULTS: 40 different drugs were separated by UPLC (ultra pressure liquid chromatography) with a run time of 5.2 min. Detection limits were below our cut-off values. Individual drug species instead of drug classes were identified; correlation with GC/MS was excellent. A high throughput, robust assay with acceptable accuracy, precision and specificity was developed. The procedure can also be used as a quantitative method with simple modifications. CONCLUSIONS: An improved, high throughput, cost-effective method for drugs of abuse screening has been implemented. GC/MS confirmations were reduced or eliminated. The new procedure is a viable alternative to our previous immunoassay method. Acceptable turn around times, an expanded menu, simplified sample preparation and analytical reliability makes this method a desirable option in the clinical laboratory setting.