According to an New York Times op-ed by radiologist David Levin, nonradiologists do poorly at reading imaging tests, failed on-site inspections one third of the time, and caused "virtually all of the increase in Medicare use of imaging and the resulting costs." Nonradiologists' share of the total dropped from 39 percent to 15 percent, according to a study, "The Effect of Imaging Guidelines on the Number and Quality of Outpatient Radiographic Examinations," published in the American Journal of Roentgenology (2000; 175:9-15). On-site imaging inspections found no deficiencies at radiologists offices but "significant deficiencies" in 78 percent of nonradiologists'offices, the study also found.
Actually, much of the research on the topic is either inconclusive or out of date, but one study does back up many of Levin's claims. One managed care plan experimented with guidelines limiting the imaging privileges of nonradiologist physicians, and saw the number of radiographic examinations drop 20-25 percent from 1995 to 1997 after years of increases.