[Immunochemical screening: manipulation, handling and interpretation errors, exemplified by benzodiazepines]

The article describes problems related to immunochemical screening-tests with special regard to benzodiazepines, which are commonly used for therapeutic purposes. Focal points are adulteration, manipulation and handling of samples, the selection of cut-off-values, specificity and cross-reactivity, influence of biotransformation and frequently observed pitfalls in the interpretation of the analytical results.