[Blood screening of benzodiazepines and tricyclic antidepressants. Results of 5 years of interhospital controls].

Pro bio Qual Association of Lyon have proposed a control which include the control for detecting benzodiazepines (BZD) and tricyclic antidepressants (ADT) since 2000. With this control, we have evaluated the specificity and the sensitivity of techniques used. We have tested the maprotiline reactivity too (tetracyclic antidepressant). We report results achieved with different immunoassay methods and their performances: specificity and sensitivity. The number of laboratories which realize these analyses is constant: these laboratories are hospital laboratories. Two methods are most common used: the fluorescence polarization immunoassay (FPIA) and the enzyme multiplied immunoassay test (EMIT). The evolution of these techniques does square with the evolution of chemistry analysers used in hospital laboratories. For the BZD, the specificity is good. For the ADT, carbamazepine at low concentration (5 mg/L) gives a positive result with FPIA Abbott assay; carbamazepine at high concentration (25 mg/L) gives a negative result with EMIT assay; phenothiazines give a positive response. For the BZD, the analyser Integra gives best results of sensitivity. Results of sensitivity obtained with the kit EMIT DAU are better than results obtained with the kit EMIT Serum. For the ADT, results of sensitivity obtained with FPIA Abbott assay seem better; the adaptation of EMIT assay on Integra analyser gives less good results. The reactivity for the BZD is very different: we can ignore a severe intoxication with alprazolam or lorazepam (response << cut off) but we can give a positive result for a therapeutic concentration of diazepam for example. With ADT, we haven't the same problem. But the reactivity for nortriptyline is less good than the reactivity for amitriptyline. So we should use a "cut off" concentration which corresponds to the best sensitivity and the best specificity.