[Uniform analyzes of drugs in urine needed for rule of law]

Drugs of abuse testing is used in various areas of society for detection and follow-up of drug use. In routine laboratory drug testing, immunoassays are employed for initial screening of specimens to indicate the presence of drugs. To confirm a positive screening test, a secondary analysis by mass spectrometry is performed. The "cut-off" is the pre-defined concentration threshold of a drug or drug metabolite above which the sample is considered positive. A reading below this level implies a negative test result. Swedish drug testing laboratories currently employ varying cut-offs to distinguish between a positive and a negative test result. Because a positive drug test may have serious legal consequences to the individual, it is of importance that testing is performed and judged equally, regardless of where it is performed. A national harmonization of cut-offs is therefore warranted. Based on data from four major Swedish drug testing laboratories, and considering the recommendations in international guidelines, a proposal for national harmonization of urine cut-offs for the most common set of drugs of abuse is presented.