Stephanie J. Marin

Our laboratory uses ELISA reagents (Immunalysis) to detect drugs of abuse in meconium. Poor specificity of immunoassay reagents for amphetamines is well characterized and as a result, specimens that test positive for amphetamines by immunoassay are routinely tested by a second analytical method to prevent false-positive results. Our ELISA screen for meconium has separate detection antibodies for amphetamine and methamphetamine. The ELISA cutoff for these drugs is 20 ng/g. All positive screen results are confirmed by GC-MS.

A single method for confirmation and quantitation of a panel of commonly prescribed benzodiazepines and metabolites, α-hydroxyalprazolam, α-hydroxyethylflurazepam, α-hydroxytriazolam, alprazolam, desalkylflurazepam, diazepam, lorazepam, midazolam, nordiazepam, oxazepam, temazepam, clonazepam, and 7-aminoclonazepam, was developed for three specimen types, urine, serum/plasma, and meconium. Quantitation was by liquid chromatography tandem-mass spectrometry (LC-MS-MS) using a Waters Alliance-Quattro Micro system. The instrument was operated in multiple reaction monitoring mode with an electrospray ionization source in positive ionization mode. The method was evaluated for recovery, imprecision, linearity, analytical measurement range, specificity, and carryover. Average recovery and imprecision (within-run, between-run, and total % CV) were within ± 15% of the target concentrations for urine (10 to 5000 ng/mL) and serum/plasma (10 to 2500 ng/mL) and within ± 20% for meconium (10 to 5000 ng/g). In all, 205 patient specimens were analyzed, and the results compared to a previous in-house gas chromatography-MS method or LC-MS-MS results from an outside laboratory. Oxazepam glucuronide was evaluated as a hydrolysis control for the urine and meconium specimens.