title: Immunoassays for drug screening in urine : Chances, challenges, and pitfalls.
abstract: Immunoassays are presently used worldwide for the rapid screening of drugs. Despite the fact that they are a highly valuable tool for the testing of legal and illicit drugs, there is a real risk of false-positive and false-negative findings and many pitfalls must be taken into account when these tests are used in an uncritical manner and without valid confirmation procedures. In a long-standing successful cooperation with a large psychiatric hospital, we checked doubtful and nonplausible immunochemical findings in urine with gas chromatography-mass spectrometry (GC-MS) confirmation methods. The reported case histories demonstrate typical pitfalls, for example, influence of changing nutritional habits, use of sweeteners (cyclamate), uncritical creatinine correction, impaired elimination, or cross-reactivities of simultaneous therapeutic medication. In accordance with national and international associations, immunoassays are recommended as a useful tool for screening. However, confirmation analysis with conclusive methods (GC-MS or liquid chromatography-MS) is unavoidable for valid substance identification, discrimination between active and inactive metabolites, detection of congeners, and accurate determination of concentrations in body fluids.
authors: Institute of Legal Medicine, Justus-Liebig-University, Frankfurter Str. 58, D-35392, Giessen, harald.f.schuetz@forens.med.uni-giessen.de.
authors: Harald
authors: H
authors: Schütz
authors: Alexandre
authors: A
authors: Paine
authors: Freidoon
authors: F
authors: Erdmann
authors: Günter
authors: G
authors: Weiler
authors: Marcel A
authors: MA
authors: Verhoff