June 21, 2018
Patient getting a CT scan
Be Well

The Scan Trap

by John Swartzberg, M.D.  

The ability to peer inside the body via imaging tests such as X-rays, CT scans and MRIs is nothing short of miraculous and has saved countless lives. That said, Americans get too many medical scans—far more, on average, than people in other industrialized countries, without necessarily getting better health outcomes. Why do we get so many imaging tests?

  • Doctors may order tests out of habit, wanting to leave no stone unturned—or out of fear of being sued if they miss something.
  • Some patients pressure doctors for scans, feeling that high-tech testing is optimal care, or just to be safe.
  • There’s an increased supply of machines, and doctors who own them or have a financial stake in the facilities have an incentive to order more scans.
  • As scanning machines become more powerful, they detect more and smaller “abnormalities.” Many of these findings are clinically insignificant but lead to more testing.
  • Medical imaging tests are also increasingly being used for screening healthy people, though there’s no evidence of benefit. For instance, “full-body” CT scans are promoted as a way to detect cancers, cardiovascular disease and many other disorders.

What’s wrong with overusing such technology, besides the huge and growing financial costs? Some of the tests, notably CT scans, expose patients to radiation, which is cumulative over a lifetime. They also frequently reveal incidental findings that lead to overtreatment.

I was reminded of this recently while working, along with my colleague William Pereira, M.D., M.P.H., on a digital Wellness Report, How to Manage Back Pain. Doctors often order MRIs to pinpoint the cause of chronic back pain. Though excellent for confirming certain diagnoses, MRIs of the spine produce far too many false alarms to be a good routine test for people with back pain. That is, the scans may reveal an abnormality that’s assumed to be the cause of the pain, but isn’t.

The fact is, MRIs find spinal abnormalities, such as a herniated disc, in most people, including those who have no back pain. Such false-positive results help explain why the rate of back surgery in the U.S. is more than twice as high as in other countries—and why, all too often, the surgery doesn’t help. In many cases, surgery corrects a “problem” that is unrelated or incidental to the cause of the pain.

It's telling that a Dutch study in the New England Journal of Medicine in March 2012, which looked at 267 patients who had been treated for sciatica and lumbar-disk herniation, found that MRIs done one year later couldn't distinguish between those who still had pain and those who were asymptomatic. That certainly makes one wonder about the diagnostic accuracy of MRI for low back pain.

My advice: Before undergoing an MRI or other medical scan, discuss the pros and cons with your doctor.