ABSTRACT
Five chromatographic and six immunoassay techniques were compared using data reported by 131 participants in the UK National External Quality Assessment Scheme for Drugs of Abuse in Urine. Twenty five samples were studied containing none or one of three concentrations of amphetamine, barbiturates, benzodiazepines, benzoylecgonine, methadone and morphine. Technique sensitivity and specificity achieved with realistic clinical samples of 25 mL vol were assessed as the percentage of true positive and true negative tests, respectively. Thin-layer chromatography was inadequate for the detection of several analytes, the sensitivity for 0.5 mg/L of benzoylecgonine being < 30%, and for 1.5 mg/L of amphetamine < 86%. Gas chromatography with mass spectrometry was significantly less sensitive than other techniques for the detection of 0.5 mg/L of benzoylecgonine (71%) and 1.5 mg/L of morphine (88%). High-performance liquid chromatography was the most sensitive for amphetamine. Immunoassays performed well when operating above their specified cut-off concentrations but, because they are directed to quinalbarbitone showed reduced cross-reactivity with amylobarbitone, the barbiturate more commonly prescribed in the UK.
Subject(s)
Chromatography/methods , Illicit Drugs/urine , Immunoassay/methods , Cross Reactions , Female , Gas Chromatography-Mass Spectrometry , Humans , Longitudinal Studies , Male , Quality Control , Technology Assessment, Biomedical , United KingdomABSTRACT
A "Centrifichem" centrifugal analyser was found using a double fluorescence/bacterial tracer method to be a source of airborne and surface contamination in the laboratory. The airborne contamination was controlled by a modification incorporating a filter. Ubiquitous surface contamination generally accompanied the processing of simulated patients' sera. Double tracer samples could be used in laboratories to assess the quality of hygiene practices in the same way as quality control samples are currently used to assess the quality of analytical performance. The findings indicated a lack of understanding of basic hygiene practices in the laboratory.
