Q&A: Neuroimaging: More False Positives than True Positives?

As the availability of diagnostic tests and treatment options grows, the medical community is left with a double-edged sword. Patient complaints are more thoroughly investigated, providing earlier diagnosis, but physicians are finding more false positives and incidental findings that may not have caused problems if left undetected, and financial resources are stretched.

To combat this, the Choosing Wisely campaign challenges medical specialties to list steps that members could take to use health care resources more effectively. The program has grown to include more than 70 medical societies.

A study that was published in Neurology looked at all neurology-related Choosing Wisely items. After categorizing the items according to neurological specialty, disease and symptoms, and tests and treatments, the researchers, led by Brian Callaghan, MD, a neurologist at the University of Michigan in Ann Arbor, found that of 370 items provided by 65 medical societies, 20% (74 items) were relevant to neurologists. Several were duplicates, which the researchers recommended be prioritized. Callaghan shared his thoughts with Diagnostic Imaging.

What led you to do this study?

We started looking at testing based on Choosing Wisely, and MRI was by far the thing that we spend the most money on. In fact, we spend more money on MRI than on procedures like electromyography (EMG) and electroencephalography (EEG). In this country, we spend more on neurology-ordered imaging than we do on neurology visits to the doctor.

Then, when you start looking at common conditions, the most common neurologic condition is probably headache. If we're trying to be more efficient, we should see where we're spending our money and what we’re spending it on. Headache neuroimaging was a natural fit. 

And what you did find?[[{"type":"media","view_mode":"media_crop","fid":"44636","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_951045364246","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"5011","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 160px; width: 160px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"Brian Callaghan, MD","typeof":"foaf:Image"}}]]

We found that we spend about a billion dollars on headache neuroimaging. And this isn't influenced by different red flags that might prompt neuroimaging. Even when we focused on the patient population least likely to need neuroimaging, such as patients with migraines, they still had an incredibly high chance of undergoing imaging.

What do you say to the patients who go to the neurologist and insist on having imaging done? And physicians who are confronted with these requests?

I think it really is a two-way street. Patients want the imaging and physicians want it, but for different reasons. Patients are worried about having a brain tumor. From a doctor's standpoint, they're scared of missing the very rare causes of headache, partly because that's how we're trained to not miss anything and partly because of some medical legal aspects. Both parties have their reasons. That's why almost 50% of patients with migraines will end up with neuroimaging after a handful of years. 

What I think people don't understand is that with [MRIs for migraines], you're much more likely to find a false positive than a true positive. Those false positives can lead to more tests and potentially even interventions that can harm. We're involved in a project right now that's going to try to show just how much harm is possible for patients getting MRIs.

What would be the next step then? 

It is a consensus that patients with common migraines shouldn't get neuroimaging, but I think there are two problems. One is the guidelines are not clear. It is also really hard to change behavior. Even if we all agree when to get neuroimaging, changing what's currently going on is something that is hard to do.

What was the goal behind the study and what message would you like people to take away from this?

I think one of the goals would be to educate patients that they should engage in a conversation with their physician about the need for these tests. We should be questioning why we're getting certain tests, and definitely in the context of headache and MRI.

Specific to headache and MRI, it's true that the yield of finding something on MRI is very low in someone with migraines, on the order of 1%. If you take healthy research volunteers, there's a very comparable yield. It's not clear that the yield in patients with migraines is any higher than people just off the street.

The Choosing Wisely guidelines are mostly the guidelines that people can all agree upon, developed by specialty societies, so they're by the very people that have the most invested in doing the tests. These are the things that most physicians agree on.