Benzodiazepine findings in blood and urine by gas chromatography and immunoassay

Gas chromatography (GC) and immunoassay techniques applied to blood and urine specimens were compared for the screening of benzodiazepines in postmortem forensic toxicology. Five hundred and six such successive postmortem cases in which both urine and peripheral blood was sent for toxicological analysis by the medical examiners were selected. The urine specimens were tested by the Emit((R)) d.a.u. Benzodiazepine Assay, and in parallel, the blood and urine specimens were screened for benzodiazepine drugs and their metabolites by an established automated dual-column GC method. The lowest number of positives (153) was obtained when immunoassay was performed without enzyme hydrolysis. When urine samples were hydrolysed before immunoassay, the number of positives increased to 175. The highest number of positives (200) was obtained in urine by GC, and the screening of blood by GC yielded 185 quantitative results. Despite the urine GC screening produced the most positives, the quantitative screening of the blood by GC appears to be the most efficient approach in postmortem forensic toxicology, considering the fact that although urine findings confirm the presence of the drug, quantitative results in urine are irrelevant to acute toxicity.