The estimated predictive value of screening for illicit drugs in the workplace.

This paper estimates the predictive values of screening tests for six illicit drugs of common concern in the workplace (amphetamines, barbiturates, cocaine, hallucinogens, marijuana, and opiates) using published information on test sensitivity and specificity and survey data on prevalence. Estimated predictive values (negative) were generally high, whereas the estimated predictive value of a positive test ranged from 1 per cent for amphetamines to 100 per cent for hallucinogens and was only 38 per cent for marijuana, the most prevalent drug.