Oates is a Boston Medical Center geriatrician who makes house calls, part of a cadre of physicians nationwide who serve a growing need of homebound seniors. He believes home visits provide more personalized, consistent care to people who might not otherwise see a doctor and can prevent hospitalizations or delay a move to a nursing home. Now the Centers for Medicare & Medi-caid Services, in a program created under the newly-affirmed Affordable Care Act, is looking at the Boston program and 15 others to see whether they also can save money. Advocates hope the results will persuade more doctors to begin seeing patients at home.