| Sumario: | AIMS: This study evaluates the suitability of gas chromatographic-mass spectrometric (GC-MS) analysis to follow-up the extent of benzodiazepine (mis)use in a Belgian prison population and compares it to other analytical strategies (e.g. screening followed by confirmation of the positive samples). DESIGN AND PARTICIPANTS: From February to August 1998, 598 persons were jailed of which 188 (31.4% of the incoming detainees) volunteered to be screened. Urine samples (530 in total) were collected on the day of arrival and after 14, 30 and 90 days of imprisonment. MEASUREMENTS: All samples were screened by EMIT(R) for benzodiazepines and analysed subsequently by GC-MS. FINDINGS: EMIT(R) screening yielded 117 (22.1%) positive samples, a number which increased to 174 (32.8%) after GC-MS analysis. Of these 174 GC-MS positive samples, 119 (68.4%) contained one benzodiazepine while for the remaining samples multiple benzodiazepine (mis)use could be demonstrated. A significant increase in benzodiazepine (mis)use was indicated only from day 0 to day 14 based on the GC-MS results but not on the immunoassay results, even when the latter were complemented with GC-MS analysis of the positively screened samples. The GC-MS data also demonstrated that benzodiazepines are mainly (mis)used by subjects on benzodiazepine prescription as almost 50% of these subjects took additional non-prescribed benzodiazepines. During GC-MS analysis other drugs were co-extracted unintentionally and chromatographed and 23.9% of the volunteers were positive for illegal drugs on the day of arrival. CONCLUSION: Immunoassay results yield an underestimation of the problem of benzodiazepine (mis)use in prison due to the high false negative rate. GC-MS analysis of all samples therefore is the recommended strategy for this type of longitudinal study as it yields more correct and detailed information than the immunoassay results.
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