[Drug screening in urine--common pitfalls in measurement and interpretation].

Nowadays immunoassays are used for the rapid screening of drugs world-wide. Despite the fact that they are a highly valuable tool for the test of legal and illicit drugs, there is a non-negligible risk of false positive and false negative findings, and many pitfalls must be taken into account when using these tests in an uncritical manner and without valid confirmation procedures. In accordance with the committee for "problems of threshold values for medical and addictive drugs" set up by German scientific societies (in particular GTFCh, DGRM and DGVM), immunoassays are recommended as a useful tool for screening. But confirmation analysis with conclusive methods (GC/MS or LC/MS) is indispensable for valid substance identification, discrimination between active and inactive metabolites, detection of escort substances and accurate determination of concentrations in body fluids.