Proficiency testing for psychoactive substances in Italy.

This paper describes the general design and main results of the Italian proficiency testing program for the analysis of psychoactive substances in urine, a long-term initiative created in 1995 on an educational basis and characterized by an innovative internet-based service for data exchange between laboratories and the organizing body. Batches of six urine samples, validated by reference laboratories, are sent every 3 months to participating laboratories, which may choose which classes of substances to test from those planned by the program panel and, within those classes, which type of analytical commitment to work on: identification of just one class (Option 1), identification of single substances (Option 2), or identification and quantification of single substances (Option 3). Comprehensive periodical reports and annual reports are provided to participants with evaluation of their performance and an annual workshop is organized to discuss technical-scientific topics related to clinical, forensic and analytical toxicology. About 200 laboratories currently participate in the program and a total of 67,059 analyses have been carried out since 1995. The mean percentage of correct results was 96.8%, with a yearly improvement of about 0.4%. The best average false positive and false negative rates were obtained for methadone (0.2% and 2.1% respectively) and cocaine (0.3% and 2.2%). The worst average false positive rates were obtained for amphetamines and opiates (3.2% and 5.0%) and worst average false negative rates for amphetamines, barbiturates and cannabinoids (17.4%, 30.7% and 19.9%).