(AP) -- CT scans, MRIs and other pricey imaging tests are often more for the doctor's benefit than the patient's, new research confirms.
Roughly one-fifth of tests that bone and joint specialists order are because a doctor fears being sued, not because the patient needs them, a first-of-its-kind study in Pennsylvania suggests.
The study comes a day after the Obama administration began a push to overhaul state medical malpractice laws as a way to reduce unnecessary tests that drive up health care costs.
"This study is a glimpse behind the curtain of what's happening in a doctor's mind," said its leader, Dr. John Flynn of Children's Hospital of Philadelphia. If doctors sense you might second-guess them or cause trouble, "you could potentially be risking more tests being done."
Results were reported Wednesday at an American Academy of Orthopedic Surgeons conference in California.
Patients expect the highest level of care and think this means the most advanced technology, Flynn said. Many patients feel better when a doctor orders lots of tests - until they get the bill.
Besides hurting your wallet and adding to health care costs, unnecessary tests can expose people to radiation that accumulates over a lifetime and can raise the risk of cancer. Ordinary X-rays are rarely a concern, but an MRI, or magnetic resonance imaging scan, can cost $1,000 or more. And super-sharp X-rays called CT scans involve relatively large radiation doses.
Yet doctors often order tests they don't really think a patient needs because they fear being sued if the diagnosis was wrong or they miss detecting a problem.
Previous studies of how often this happens have relied on doctor surveys. This is the first one to enlist doctors in advance to track their decisions over time.
It involved 72 orthopedic surgeons throughout Pennsylvania who tracked tests they ordered on 2,068 patients, mostly adults, in ordinary office visits, emergency rooms and other settings. Doctors checked a box saying a test was either required for clinical care or done "for defensive reasons."
Defensive imaging accounted for 20 percent of total tests - 11 percent of X-rays, 38 percent of MRIs, 33 percent of CT scans, 57 percent of bone scans and 53 percent of ultrasounds.
Defensive medicine also accounted for 35 percent of costs, nearly all of it from MRIs.
One example: a torn meniscus, a knee cartilage injury that is a leading reason for knee surgery. Studies have shown that a doctor's judgment based on symptoms and an exam is even better than an MRI to diagnose the condition. Yet patients hardly ever go to surgery without having the imaging test, Flynn said.
Surprisingly, the study found that newer doctors were less likely to be defensive.
"That's counterintuitive," Flynn said. "You would expect when you're new in practice, not as trustful of your clinical judgment, you'd order more."
Doctors who have been sued in the last five years were more likely to order tests defensively, said Robert Miller, a Temple University medical student who helped lead the study and presented the results at the conference.
Dr. Lawrence Wells, a Philadelphia surgeon who participated in the study, said doctors learn to develop "a radar" for problem patients.
"It's disheartening" to be sued, he said. "Someone's accusing you of a bad outcome or a wrong," and that can affect how a doctor behaves the next time he sees a similar case.
Patients need to trust their doctor's judgment on what is needed, Wells said.
On Tuesday, Obama made a budget proposal that includes money to help states rewrite malpractice laws. Possible measures include caps on awards. The administration also has proposed health courts where specially trained judges rather than juries would decide such cases.
Questions to ask about a medical test:
-Is it truly needed? How will it change my care?
-Have you or another doctor done this test on me before?
-Does the test involve much radiation and is there an alternative that does not?
-How many images are needed?
-Do you have a financial stake in the machines that will be used?
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Orthopedics group: http://www.aaos.org/
Consumer information: http://www.radiologyinfo.org and http://tinyurl.com/2wv5fg