Pink, I have no ideas what the standards are in Great Britain, but over here in America, a drug screen would not be a part of a standard blood test for a 15-year-old unless there were a suspicion of illicit drug use/illicit drug interactions causing medical trouble. Or unless it were expressly requested by his parents. Your country's privacy laws are different from ours, too, and so I don't know what they can reveal and what they cannot. Here the confidentiality age varies among states.