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CT Scans: Patients Often Unaware of Possible Risks


Doctors don’t always discuss the risks of CT scans with patients. One researcher explains why and the implications for radiologists.

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That’s what researchers from the Denver Veteran Affairs Medical Center wanted to find out. They undertook a survey to determine the level of patient understanding of CT risks. Diagnostic Imaging spoke with one of the authors, general internist Tanner J. Caverly, MD, about the survey and its findings.

Why were you interested in looking at whether doctors were having a benefits versus risk conversation with their patients when ordering a CT scan?

I have a general interest in how to communicate risks and benefits for patients. The senior author on the paper, Chad Stickrath, is also interested in learning about unnecessary testing. Since we didn’t see a lot in the literature about what is actually communicated in real practice about the risks of CT scans, we thought we’d take a closer look at that at our specific center.

We also thought that even if such discussions were taking place, they were probably fairly superficial, given the time constraints and the lack of comfort physicians generally have about talking about these risks.

Why might these conversations not be taking place, or if they are, why are they superficial?

I think the first difficulty is that these are the estimates of the harms from CT scans are pretty unknown and hard to communicate. The risk from radiation is based on estimates from atomic bomb data and observational trials, and it’s hard to relate that to what we’re doing when giving an imaging test. The estimates are just estimates and it’s not necessarily comfortable for us to bring those down into hard specific numbers. There’s so much uncertainty around them. So that’s hard to communicate.

In addition, the other big harm that we were interested in was the chance of finding something incidentally, a spot on the lung or on the kidney or somewhere else that wasn’t causing any problems and potentially would never cause any problems. But once you see something on a CT scan, we generally do something about it.

Treating the incidental findings can ultimately cause complications. If you pursue these things, you can end up doing a biopsy and doing something that may cause harm. It’s unclear whether following these findings are beneficial.

So, are the patients asking these questions from the radiologists instead? And if so, how are the radiologists responding?

We found that patients who reported not hearing about risks and benefits from the ordering physician were more likely to feel they needed more information about potential risks. So, a substantial proportion of patients about to undergo a CT seem to desire more information about the risks of CT than they are getting.

I think that different patients seek out this information in different ways. One way is to ask the radiologist, if the radiologist is available. Based on conversations I have had with radiologists at the University of Colorado, I do think they get many questions from patients and questions about radiation risk in particular.

There is a group of radiologists here who are very interested in better communicating the risks of radiation to patients. They have put together a patient information card for interested patients awaiting imaging tests and I have played a small part in that effort here. This group is also engaging different groups of clinicians to teach them the basics of radiation risk and try to get them more comfortable discussing this information with patients. They have actually created a very interesting "Radiology Dose-Risk Smartcard."

Did you qualify if the CT scans were ordered by family physicians or specialists and, if so, was there a difference in reported discussions with patients?

We did ask who had ordered the CT scan. There were emergency providers, specialist providers, primary care providers and I think “other,” but there weren’t really any other physicians that kind of encompassed everybody.

We did try to analyze if there were differences based on the order and provider and we didn’t see any statistically significant differences. There were no trends but maybe we didn’t have a large enough sample. We didn’t have enough patients to be splitting it by who ordered the tests.

You found that even if the conversations are taking place, they don’t seem to be making a difference in how patients are making decisions. Why might this be?

We didn’t actually listen in on the conversation obviously, but according to the patients when they responded, “Yes, my doctor talked about both the risks and benefits,” they were no more knowledgeable.

We asked the patients to rate the level of radiation that comes from chest X-rays, MRI, background radiation from living for one year in Colorado, and getting a CT scan. We didn’t expect patients to know the doses of the CT scans, but since most people are familiar with chest X-rays and given they have much lower radiation than CT scans, if patients didn’t know this, it would show that they didn’t know much about the radiation at all.

As we reported, only 37 percent said that the CT scan had more radiation than a chest X-ray. From that specific piece of knowledge people who had had a risk/benefit discussion with their physicians really didn’t do any better when ranking CT over chest X-ray of the people who reported no such conversation.

So, how can we improve these conversations then?

There are two avenues. I think the most important one, and it cuts across more than just the CT scan, is that we need to have empowered patients who are asking questions, taking charge.

I think physicians generally do like talking about this type of information, but sometimes, given time constraints, they may not be able to talk about everything that’s important. So, I think it’s important for patients ask questions like:

  • What are the risks of getting a CT scan?
  • What are the benefits of this test for me at this time?
  • Are there any other options?
  • Is not getting a CT scan an option?
  • What happens if I don’t get it?
  • What do you think the risks are of not getting the tests?

I think they’ll have a much more enlightened view of the need for the test or whether it’s a close call, whether they can wait a couple of months or couple of weeks before getting that test, and see how their symptoms evolve. It’s important that they are as informed as possible, and asking these questions really will do the trick.

The other avenue is getting physicians more comfortable with these discussions. I think some of it is just the lack of awareness of radiation and other harms of CT scans. We generally view CT scans as pretty benign, which they are. These risks are generally small, but I don’t think we can presume how patients view them. Different patients may view the risks benefit ratio differently.

What are you going to do next?

My research really revolves around how to communicate risks and benefits to patients and also how physicians think about risks and benefits. I’m going to continue to delve into how we can really get communicating risks versus benefits in the routine practice, how to educate those to think more clearly about the risks and the benefits of the interventions they’re suggesting. This is not only for CT scans but with other testing as well.

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