According to Ron Waldorf, the SafetyScope's designer, the device gives the most effective reading when the worker's data can be compared to a previous reading obtained when he or she was completely unimpaired. Such a baseline reading could be gathered at the worker's initial doctor's examination. Waldorf said it's difficult to nail down an exact accuracy rate, because a person's tolerance for drugs, alcohol, and fatigue are extremely variable based on weight and other factors. Apart from the issue of accuracy, Waldorf said the SafetyScope makes an ideal alternative to urine or blood drug tests for reasons of privacy and fairness. It's invasive, it's obviously demeaning, and it doesn't address the actual issue of impairment.
Urine tests are really limited in that they only look for five to nine substances.
But there are so many things that can impair a person, like fatigue, prescription drugs, what have you. The American Civil Liberties Union considers most workplace drug testing an invasion of privacy and a waste of money. Graham Boyd, director of the national ACLU's drug litigation project, points out that urine tests can be faulty and inaccurate. The drug testing industry claims that drug tests reduce accidents and improve productivity. But there's been no significant studies showing that drug testing has an appreciable impact on safety or productivity.