About 28 percent of the orders for three services at three hospitals were judged to be at least partially defensive by the physicians who ordered them.

The overuse of medical tests and procedures driven by a fear of malpractice lawsuits, commonly known as defensive medicine, has been estimated to cost $46 billion annually in the U.S., although those costs have been measured indirectly.

The authors estimated the cost of defensive medicine on three services - tests, procedures or hospitalizations - by asking physicians to estimate the defensiveness of their own orders. The authors invited 42 hospitalist physicians to complete a survey, which 36 physicians did and rated 4,215 orders for 769 patients in the research letter.

Of the orders, 28 percent were rated as defensive and the mean cost was $1,695 per patient, of which $226 (13 percent) was defensive. Completely defensive orders represented about 2.9 percent of costs, mostly because of additional hospital days.

"In conclusion, although a large portion of hospital orders had some defensive component, our study found that few orders were completely defensive and that physicians' attitudes about defensive medicine did not correlate with cost. Our findings suggest that only a small portion of medical costs might be reduced by tort reform."

The study is published in JAMA Internal Medicine.