Incidental findings

If you could have a full-body CT scan to look for anything that might signal a health issue, would you do it? Would you think it was worthwhile even if everything checked out OK?

To many American health consumers, screening invariably is good, especially if there’s a chance it might pick up potential problems in their early stages. A newly published study suggests, however, that most of the time the medical benefit is considerably less than people think.

The study appears in the latest issue of the Archives of Internal Medicine and involved more than 1,400 imaging exams that were conducted over a three-month period at the Mayo Clinic in conjunction with clinical studies in which the patients were enrolled. The study’s authors tracked how many of these exams resulted in an incidental finding, or the discovery of something unrelated to the scan’s original purpose and that might have triggered some form of followup.

Here’s how the results stacked up: Of the 1,426 medical imaging exams that were reviewed for the study, 567 cases, or just under 40 percent, yielded an incidental finding. About 6 percent of these incidental findings – 35 in all – led to further clinical action. There was clear medical benefit for six of the cases that involved followup but a clear medical burden for three of them. In the rest of the cases the balance between burden and benefit was unclear, the study’s authors concluded.

The study’s authors noted that the likelihood of an incidental finding appeared to increase with the patient’s age. CT scans of the abdomen and pelvis, CT scans of the chest and MRI exams of the head were the most likely to produce incidental findings. Ultrasound and nuclear medicine scan yielded the fewest, accounting for just 16 of the 567 cases uncovered by the study reviewers.

One of the drawbacks of this particular study is that the determination of burden vs. benefit is subjective. Also, the study was limited to three months’ worth of data from a single institution involving research patients, and the followup data on patients may have been incomplete.

Nevertheless, it helps assign some numbers to two of medicine’s more perplexing questions: How often do incidental findings show up, and how often do these findings turn out to be significant?

Some of the incidental findings in this particular study were of no small importance. Four of them turned out to be a previously unsuspected tumor; in another case a fungal infection was uncovered. Much of the time, however, a so-called incidentaloma triggered further investigation but failed to result in any firm diagnosis. Although most of the followup was minimal, a handful of patients underwent additional medical imaging, biopsies, laparoscopy and even open surgery, yet gained no clear benefit from it.

An accompanying editorial to the Archives study asks the question, “Now what?” and suggests the development of guidelines for how best to handle incidental findings when they arise, especially during the course of clinical research. Dr. Bernard Lo writes:

There may be a tendency to overstate the benefits because vivid cases of clear benefit are salient in human memory. However, the burdens of follow-up testing should not be understated; psychological risk, inconvenience, and radiation risk due to serial computed tomographic scans should not be downplayed.

Maybe to some people it’s worth it to know an anomaly has been discovered, checked out and turned out to be nothing. Benefit, after all, is often in the eye of the beholder. And whether an intervention is needless sometimes can’t be determined until after the fact.

We tend to focus on how medicine will help us, however, and less on the possibility that it might be useless or even downright harmful. Incidental findings are particularly challenging because they can’t always be ignored; once something unexpected turns up, the clinician and patient have to decide what to do about it. Although it’s reasonable for these decisions to be guided by the likelihood of benefit, it’s apparent from this study that further investigation of an incidental finding often has a questionable return on investment. Sometimes incidental findings are just that – incidental findings.

Photo: Wikimedia Commons

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