Retailers and bankers are already familiar with the concept. And soon doctors in Tennessee could learn what it means to get a call from the mystery shopper. Tennessee is among nine states where some physicians' offices could receive cold telephone calls from researchers posing as patients in a bid to gauge whether primary-care doctors are willing to see patients on Medicaid or private insurance. "We're working to expand access to primary care nationally while also tracking the success of those efforts at the community level," said Richard Kronick, a deputy assistant secretary with the U.S. Department of Health and Human Services. Under the proposal, which is up for public comment for much of this month, the mystery shopper program would try to gauge how quickly patients are able to get an appointment — especially to see a doctor for the first time.