Between a third and a half of six common diagnostic tests for Medicare patients, including nuclear imaging stress tests, were repeated on patients from 2004 to 2006, according to a study that examined the records of a sample of patients. Researchers reported their results in the Archives of Internal Medicine. Retesting can be medically appropriate, including as a way to monitor whether treatments are working, but it can be a factor in overdiagnosis and adds to health care costs, experts said.

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