Sunday, December 15, 2013

"By the way...": The pros and cons of incidental findings

Melissa Healy wrote a very interesting story for the LA Times last week on what happens when a medical test reports something unexpected.You're looking for pneumonia and the chest x-ray shows a cancer in the spine, but you don't know where it came from. A head CT to rule out subdural hematoma after a head injury shows an aneurysm...that might or might not cause trouble one day. These "incidental findings" are disturbingly common.

High tech imaging tests like CT scans and MRIs are particularly prone to this because they are not very specific in their field of view and provide a huge amount of information. If you get a CT of the abdomen to look at the liver, you're going to get all sorts of information about the gallbladder, stomach, intestines, kidneys, pancreas, etc. even if you don't want it. In my experience, lungs and brains are particularly full of findings of "uncertain significance" that are time consuming, costly and difficult to evaluate. They certainly induce a huge amount of anxiety in the patient.Whole genome studies are going to be even worse. The vast majority of genetic information in a person is not interpretable with anything like the accuracy required for clinical decision making.

The new that stimulated Healy's article was that the Presidential Committee for the Study of Bioethical Issues said professional organizations need to start writing guidelines for how to deal with these incidental results. In other words, we should stop treating them like they are not anticipated - we know we are going to get them even if we don't ask for them, so we better make a plan.

I'm all for coming up with guidance on this tricky issue, especially in cases where the consequences of over-diagnosis and unnecessary work-ups are high and the benefits are low. 

The unintended uses of diagnostic tests have a few other upsides to keep in mind, though. They can be used for public health surveillance to help develop strategies for the whole population of patients. This is done routinely with infectious disease tests, for instance, to alert us to new outbreaks.  More recently, we have been systematically scanning commonly done blood and urine chemistry tests to identify patients with undiagnosed diabetes and kidney disease. In the case of chronic kidney damage especially, even the doctors don't always recognize the condition as present. By using an automated system to monitor laboratory results, we can identify patients who need extra attention, reach out to them, connect them to the resources they need and prevent emergencies and other complications.

If you have thoughts on this issue, do leave a comment!

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