Comparison of different immunoassays and GC-MS screening of benzodiazepines in urine

A total of 53 urine samples were tested by different immunoassay methods and by gas chromatography/mass spectrometry to determine repeatability of the different methods and to assess whether the immunoassays performed on samples obtained from elderly patients of the emergency section could be considered as reliable enough for identifying a benzodiazepine consumption. Repeatability was excellent for GC/MS and good for immunoassays. The specificity was not different for the three immunoassays (96%). The sensitivity varied from 36, 64 to 75% for OnLine, RIA Immunalysis and RIA DPC, respectively. An other difference between immunoassays and GC/MS was the ability of GC/MS to detect lorazepam and low concentrations of benzodiazepines whereas immunoassays did not.