Wednesday, January 11, 2012

Curbing overuse of CT scans

The urban public hospital where I completed most of my training as a medical student had a single CT scanner. To ensure that this precious resource was put to effective use, any physician ordering a non-emergent CT scan was required to personally present the patient's case to the on-call Radiology fellow and explain how the result of the scan would potentially change management. Since my attending surgeons were usually too busy to trudge down to the Radiology suite, they deputized their residents to do so, and most of the time my residents passed this thankless task down to the students. Thus, my classmates and I learned early on the difference between appropriate and inappropriate reasons for ordering CT scans.

Today, the widespread availability of CT scanners has made this sort of explicit rationing uncommon in the U.S. In fact, an editorial published last year in AFP reviewed the accumulating evidence that CT scans are highly overused in current medical practice, which puts patients at unnecessary risk of radiation-induced cancers and detection of incidental findings that can lead to overdiagnosis and overtreatment. Identifying overuse of CT scans often isn't easy, though. And some might argue that increasing use of CT scans may have the positive effect of improving diagnosis of common symptoms, allowing physicians to institute appropriate management of serious conditions more quickly.

Family physicians Andrew Coco and David O'Gurek investigated this possibility in a research study published recently in the Journal of the American Board of Family Medicine. They analyzed data on common chest symptom-related emergency department visits from the National Hospital Ambulatory Medical Care Survey from 1997 to 1999 and 2005 to 2007. Unsurprisingly, the proportion of these visits in which a CT scan was performed rose from 2.1% to 11.5% during this time period. However, the proportion of visits that resulted in a clinically significant diagnosis (pulmonary embolism, acute coronary syndrome or MI, heart failure, pneumonia, pleural effusion) actually fell slightly, challenging that notion that increased CT utilization leads to improved detection and treatment of serious health conditions.

In their AFP editorial, Drs. Diana Miglioretti and Rebecca Smith-Bindman recommend that physicians and referring clinicians take several steps to reduce harms from CT scan overuse:

1. Use CT only when it is likely to enhance patient health or change clinical care.
2. When CT is necessary, apply the ALARA (as low as reasonably achievable) principle to radiation doses.
3. Inform patients of CT risks before imaging.
4. Monitor individual exposure over time and provide the information to patients.

Since 2007, AFP has published a series of articles in collaboration with the American College of Radiology on appropriate criteria for diagnostic imaging (including CT) in specific clinical situations. The ACR Appropriateness Criteria are periodically updated, and current versions are available on the ACR website.

1 comment:

  1. Great post on "Curbing Overuse of CT Scans". The unfortunate reality is that this study by Coco and O'Gurek almost certainly underestimates the true magnitude of the problem. The fact that they found more than a 5-fold increase in the number of CT scans done during the study period for chest symptom-related emergency department visits is almost certainly due to expanding the "umbrella" of patient complaints that are felt to "merit" a scan. These days it seems like patients presenting to the ED get scanned almost routinely - with natural consequence that the prevalence of true significant pulmonary embolism in the population now presenting to the ED is far less than it used to be. The probable reason that mortality has decreased from PE with increased use of CT scanning is that milder and milder cases are being found. Do we have any idea of the meaning of a small perfusion defect that is picked up in a patient with relatively unconvincing symptoms who in years past would never have gotten scanned? I wonder how many of us (who perceive ourselves to be "healthy") would be found to have small perfusion defects if we were all scanned? This phenomenon (well described by Gilbert Welch in his book, "Overdiagnosed") is pervasive in more and more of what we do. The better our diagnostic tools get (from the incredible technological advances that keep coming) - the more we pick up smaller and smaller "abnormalities" that may or may not have clinical consequences. Yet when each of the thousands of patients with atypical chest discomfort who present to EDs get CT scanned - some of them (if only by chance) will turn out to have small (and probably clinically insignificant) perfusion defects - which of course then have to be treated. Result: Much lower likelihood of benefit in these much lower risk patients - yet the likelihood of adverse effects (which with longterm anticoagulation is not inconsequential) remains the same in all of these subjects who are now turned into patients ....

    FINALLY - I'd like to add to the excellent recommendations of Drs. Miglioretti and Smith-Bindman in their AFP Editorial by saying that not only is it important to "inform patients of CT risks before imaging" - but I feel it essential to specify these risks in terms of numerical likelihood that the CT scan they are about to get may actually cause a cancer in the future. We also need to emphasize to parents that children (given their rapid growth spurts) are the segment of our population at highest risk of developing a malignancy down the road because of excessive CT scan radiation. Patient input should be actively considered in making the decision of whether or not a CT scan is truly needed for the case at hand.

    Clearly - the CT scan has been an amazing invention that has helped tremendously in the diagnosis of many medical conditions. But in addition to expense, its overuse has potential for many adverse effects - which in lower-risk groups may at times outweigh potential benefits of this diagnostic tool.

    Ken Grauer, MD (ekgpress@mac.com)

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