[fuzxi]

Medical Review Officers actually have access to prescription histories. I'm not entirely clear on how it works as I haven't personally seen that end, but they can verify non-negative results without speaking to the donor and report the result as negative (clean) to the company. They only need to speak to the donor if there's a non-negative result and they have no prescriptions that could cause a false positive for that. Also the MRO contacts the donor directly using the information on the chain of custody; the employer is never made aware that there's something abnormal about the sample.