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Journal of the American College of Cardiology

Clinical Articles, News & Views

Increase in advanced diagnostic imaging and radiation exposure

Among six large US integrated health care systems between 1996 and 2010 there was a substantial increase in the use of advanced diagnostic imaging, as well as a substantial increase in estimated radiation exposure, according to a study published recently in the Journal of the American College of Cardiology.1

Dr Rebecca Smith-Bindman (University of California, San Francisco), and colleagues, conducted the study which showed approximately a tripling of the use of computed tomography and nearly a quadrupling of the use of magnetic resonance imaging.  The study was designed to estimate trends in imaging utilisation and associated radiation exposure among members of integrated health care systems. It consisted of an analysis of electronic records of members of six large integrated health systems from different regions of the United States.

Review of medical records allowed estimation of radiation exposure from selected tests. Between 1 million and 2 million member-patients were included each year from 1996 to 2010. Enrollees underwent a total of 30.9 million imaging examinations during the study period, reflecting an average of 1.18 tests per person per year, of which 35% involved advanced diagnostic imaging (i.e., computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine, and ultrasound).

The researchers found that use of radiography and angiography/fluoroscopy rates were relatively stable over time: radiography increased 1.2% per year, and angiography/fluoroscopy decreased 1.3% per year. “In contrast, the utilisation of advanced diagnostic imaging changed markedly. Computed tomography examinations tripled…MRIs quadrupled…ultrasounds approximately doubled over the same period… Nuclear medicine rates decreased…although after 2004, positron emission tomography (PET) imaging rates increased from 0.24 per 1,000 enrollees to 3.6 per 1,000 enrollees, 57% annual growth.”

Increase in radiation exposure

The authors also found that the increase in the utilisation of CT was associated with an increase in estimated exposure to radiation, with the average per capita effective dose increasing from 1.2 mSv in 1996 to 2.3 mSv in 2010. The percent of enrollees who received high (> 20-30 mSv) or very high (> 50 mSv) radiation exposure during a given year also approximately doubled across study years.

The researchers write that the “increase in imaging use over this period was likely driven by many factors, including improvements in the technology that have led to expansion of clinical applications, patient- and physician-generated demand, defensive medical practices, and medical uncertainly—all factors that would be expected to influence utilization across all systems of medical care.”

“The increase in use of advanced diagnostic imaging has almost certainly contributed to both improved patient care processes and outcomes, but there are remarkably few data to quantify the benefits of imaging. Given the high costs of imaging—estimated at $100 billion annually—and the potential risks of cancer and other harms, these benefits should be quantified and evidence-based guidelines for using imaging should be developed that clearly balance benefits against financial costs and health risk.”

“Most studies that have evaluated patterns of diagnostic imaging have assessed insurance claims for fee-for-service insured populations where financial incentives encourage imaging. No large, multisite studies have assessed imaging trends in integrated health care delivery systems that are clinically and fiscally accountable for the outcomes and health status of the population served. Understanding imaging utilization and associated radiation exposure in these settings could help us determine how much of the increase in imaging may be independent of direct financial incentives,” the researchers write.

Patient exposure deemed “non-trivial”

In an accompanying editorial, Boston doctors write that while the data from this study and another recent report indicate that a nontrivial number of patients in the United States receive a high or very high annual exposure to ionizing radiation from imaging studies in a given year, “these data are not linked to clinical outcomes and do not reveal whether the radiation risks from these imaging studies are outweighed by the health benefits provided by the diagnostic information obtained.”

“The data also cannot address how much of this testing is driven by defensive practice styles due to concerns about malpractice. They do, however, suggest that clinicians need to consider—and discuss with their patients—radiation risks when ordering diagnostic tests, possibly taking into account the cumulative radiation exposure a patient has received in recent months or years.”

“Furthermore, the radiation risks and financial costs of advanced diagnostic imaging clearly warrant more research, including studies using informatics infrastructures such as that used by Smith-Bindman et al, to enhance decision support to guide the use of these technologies.”

References

1. Smith-Bindman R, Miglioretti DL, Johnson E, et al. Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996-2010. JAMA 2012;307:2400–9. http://dx.doi.org/10.1001/jama.2012.5960/

2. O’Connor GT, Hatabu H. Lung cancer screening, radiation, risks, benefits, and uncertainty. JAMA 2012;307:2434–5. http://dx.doi.org/10.1001/jama.2012.6096/

Published on: July 24, 2012

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