Industrial employee drug screening: a blind study of laboratory performance using commercially prepared controls

Reference laboratories are an integral component of any industrial employee drug screening program. We evaluated the performance and accuracy of the reference laboratories used by Rockwell International, a large industrial employer with an active drug screening program. A total of 829 commercially prepared control samples containing drugs of abuse, over-the-counter drugs, and analytes found in the normal employee population were disguised as routine submissions to reference laboratories used by nine Rockwell facilities. Analyses of results included compilation of false-positive and false-negative errors per drug per laboratory and a correlation of errors with preliminary and confirmation methods. Error rates of 2% false-positive results and 20% false-negative results were found for all laboratories. The errors were not limited to any one technique nor to any particular drug. The error rates observed suggest the need for routine blind testing programs and increased interaction between industry and laboratories.