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Use of Diagnostic Imaging Studies and Associated Radiation Exposure for Patients Enrolled in Large Integrated Health Care Systems, 1996-2010
Study Questions:
What trends in imaging utilization and associated radiation exposure are evident among members of integrated health care systems?
Methods:
A retrospective analysis of electronic records was conducted of members of six large integrated health systems from different regions of the United States. Review of medical records allowed direct estimation of radiation exposure from selected tests. Between 1 million and 2 million member-patients were included each year from 1996 to 2010. Advanced diagnostic imaging rates and cumulative annual radiation exposure from medical imaging were estimated.
Results:
During the 15-year study period, enrollees underwent a total of 30.9 million imaging examinations (25.8 million person-years), reflecting 1.18 tests (95% confidence interval [CI], 1.17-1.19) per person per year, of which 35% were for advanced diagnostic imaging (computed tomography [CT], magnetic resonance imaging [MRI], nuclear medicine, and ultrasound). Use of advanced diagnostic imaging increased from 1996 to 2010; CT examinations increased from 52 per 1,000 enrollees in 1996 to 149 per 1,000 in 2010, 7.8% annual increase (95% CI, 5.8%-9.8%); MRI use increased from 17 to 65 per 1,000 enrollees, 10% annual growth (95% CI, 3.3%-16.5%); and ultrasound rates increased from 134 to 230 per 1,000 enrollees, 3.9% annual growth (95% CI, 3.0%-4.9%). Although nuclear medicine use decreased from 32 to 21 per 1,000 enrollees, 3% annual decline (95% CI, 7.7% decline to 1.3% increase), PET imaging rates increased after 2004 from 0.24 to 3.6 per 1,000 enrollees, 57% annual growth. Although imaging use increased within all health systems, the adoption of different modalities for anatomic area assessment varied. Increased use of CT between 1996 and 2010 resulted in increased radiation exposure for enrollees, with a doubling in the mean per capita effective dose (1.2 mSv vs. 2.3 mSv) and the proportion of enrollees who received high (>20-50 mSv) exposure (1.2% vs. 2.5%) and very high (>50 mSv) annual radiation exposure (0.6% vs. 1.4%). By 2010, 6.8% of enrollees who underwent imaging received high annual radiation exposure (>20-50 mSv) and 3.9% received very high annual exposure (>50 mSv).
Conclusions:
Within integrated health care systems, there was a large increase in the rate of advanced diagnostic imaging and of the associated radiation exposure between 1996 and 2010.
Perspective:
This study shows an increase in the use of advanced diagnostic imaging studies among large integrated health care systems that parallel (albeit perhaps to a somewhat lesser degree) those observed among fee-for-service models of care. Although it is difficult to quantify, the use of advanced imaging likely has some beneficial role in patient care and outcomes. However, it is likely that multiple factors influence the rates of use, including but not limited to patient outcomes. Both the cost and radiation exposure associated with advanced diagnostic tests suggest that attention should be paid to criteria for their appropriate use, with attempts to minimize unnecessary testing and unnecessary radiation exposure.
Keywords: Patient Care, Tomography, Diagnostic Imaging, Medical Records, Magnetic Resonance Imaging, United States, Nuclear Medicine, Systems Integration
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