The New England Journal of Medicine study shows that some of the most popular tests performed - nuclear stress tests, CT scans of the abdomen, pelvis and chest - also provide some of the largest doses of ionizing radiation. MRI, also popular, does not use radiation. As many as 4 million adults under age 65 per year, Fazel estimates, are getting high doses of radiation that could put them in danger in the long term.
Although elderly patients are likely to get more tests, Fazel's study includes some striking data on how many tests even young people get. His research focused on three years' worth of United Healthcare claims data from five major cities, a population of nearly 1 million nonelderly adults. Seven in 10 of people ages 18 to 64 got at least one test over three years and nearly half of those between 18 and 34 got a test. Sometimes, patients get repeated tests by different doctors who don't know the patient has already been scanned. Newer scans - some that use reduced levels of radiation - tend not to replace older tests, just supplement them.
Though the annual average radiation exposure from the tests was low, researchers found about 20 percent of patients were exposed to moderate radiation doses and 2 percent were exposed to high levels. Nearly a quarter of the radiation people received came from CT scans to the heart, so-called "super X-rays" that provide 3-D pictures. And cumulative imaging-related radiation over time, researchers said, can account for 2 percent of cancers.
Congress enacted limits in 2006 to curtail Medicare spending on medical tests and scans, and private insurers have started requiring pre-authorization before some of the more advanced CT scans. A Government Accountability Office report last year showed a 12 percent decline in imaging spending from $13.8 billion in 2006 to $12.1 billion in 2007. But over the same period, the use of CT scans and MRIs continued to rise.
Jean Marshall, a health economist at Georgetown University who has studied spending patterns, said the health care system's fee-for-service model, in which doctors are paid for each service they perform, encourages unnecessary tests. Some doctors who order imaging tests own the equipment and can be reimbursed at both ends. Marshall said she wasn't surprised that the number of tests continued to rise as the reimbursements went down.
"The reimbursement system needs to be changed," Mitchell said, "because it's given them all the wrong incentives." Reforming the way tests are reimbursed, she said, is a touchy subject.
