DEFICIENT PERFORMANCE OF DRUGS OF ABUSE TESTING IN SWEDEN - AN EXTERNAL CONTROL STUDY

Testing for drugs of abuse in urine is usually performed in two steps; after initial screening positive findings are confirmed with specific chromatographic techniques. The use of different methods with differe nt cut-off levels, may lead to variable results in a test sample conta ining a drug. Sixty-eight Swedish laboratories were enrolled in an ext ernal quality study and received three control samples. The laboratori es were instructed to perform only in-house tests for amphetamines, be nzodiazepines, cannabinoids, cocaine and opiates. Nineteen out of the 68 laboratories reported fully correct results. Thirty reported one or more false positive drug findings. One laboratory performing confirma tion with gas chromatography-mass spectrometry reported a false positi ve finding of amphetamines in the sample containing ephedrine. Since t esting for drugs of abuse in urine is a delicate matter, with both med ical and legal implications, such testing should be performed with a z ero rate of false positive results. Routine use of specific methods fo r confirmation should be used since performance of these laboratories was better in this study. It is concluded that there is a need to cont inuously measure the level of quality of laboratories by a program for external quality control.