No DOt tests do not follow except: There are reporting agencies that do nothing but collect all your employement history. If a company pays to belong to one of these companies they will do a background search for you. The main company used to be called DAC but I think they changed there name a couple years back. If your company uses one of these companies you will have to sign a form authorizing them to release your info to your prospestive new employer.
Also. If you ever test positive at a company never use that company as reference for any new job applications because that company will release any positive drug tests.