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What were the trends in medical imaging from 2000 through 2016 in the United States and Ontario, Canada?
In this retrospective cohort study of 135 million imaging examinations conducted in 7 US integrated health care systems and in Ontario, annual growth in imaging rates among US adults and older adults slowed over time for computed tomography (CT; from an 11.6% annual percentage increase among adults and 9.5% among older adults in 2000-2006 to 3.7% among adults in 2013-2016 and 5.2% among older adults in 2014-2016) and for magnetic resonance imaging (MRI; from 11.4% in 2000-2004 in adults and 11.3% in 2000-2005 in older adults to 1.3% in 2007-2016 in adults and 2.2% in 2005-2016 in older adults). Patterns in Ontario were similar. Among children, annual growth for CT stabilized or declined (United States: from 10.1% in 2000-2005 to 0.8% in 2013-2016; Ontario: from 3.3% in 2000-2006 to −5.3% in 2006-2016), but patterns for MRI were similar to adults. Changes in annual growth in ultrasound were smaller among adults and children in the United States and Ontario.
From 2000 to 2016 in 7 US integrated health care systems and Ontario, CT and MRI rates continued to increase among adults, but at a slower pace in more recent years compared with earlier years; in children, CT rates stabilized or declined in recent years.
Medical imaging increased rapidly from 2000 to 2006, but trends in recent years have not been analyzed.
To evaluate recent trends in medical imaging.
Design, Setting, and Participants
Retrospective cohort study of patterns of medical imaging between 2000 and 2016 among 16 million to 21 million patients enrolled annually in 7 US integrated and mixed-model insurance health care systems and for individuals receiving care in Ontario, Canada.
Calendar year and country (United States vs Canada).
Main Outcomes and Measures
Use of computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and nuclear medicine imaging. Annual and relative imaging rates by imaging modality, country, and age (children [<18 years], adults [18-64 years], and older adults [≥65 years]).
Overall, 135 774 532 imaging examinations were included; 5 439 874 (4%) in children, 89 635 312 (66%) in adults, and 40 699 346 (30%) in older adults. Among adults and older adults, imaging rates were significantly higher in 2016 vs 2000 for all imaging modalities other than nuclear medicine. For example, among older adults, CT imaging rates were 428 per 1000 person-years in 2016 vs 204 per 1000 in 2000 in US health care systems and 409 per 1000 vs 161 per 1000 in Ontario; for MRI, 139 per 1000 vs 62 per 1000 in the United States and 89 per 1000 vs 13 per 1000 in Ontario; and for ultrasound, 495 per 1000 vs 324 per 1000 in the United States and 580 per 1000 vs 332 per 1000 in Ontario. Annual growth in imaging rates among US adults and older adults slowed over time for CT (from an 11.6% annual percentage increase among adults and 9.5% among older adults in 2000-2006 to 3.7% among adults in 2013-2016 and 5.2% among older adults in 2014-2016) and for MRI (from 11.4% in 2000-2004 in adults and 11.3% in 2000-2005 in older adults to 1.3% in 2007-2016 in adults and 2.2% in 2005-2016 in older adults). Patterns in Ontario were similar. Among children, annual growth for CT stabilized or declined (United States: from 10.1% in 2000-2005 to 0.8% in 2013-2016; Ontario: from 3.3% in 2000-2006 to −5.3% in 2006-2016), but patterns for MRI were similar to adults. Changes in annual growth in ultrasound were smaller among adults and children in the United States and Ontario compared with CT and MRI. Nuclear medicine imaging declined in adults and children after 2006.
Conclusions and Relevance
From 2000 to 2016 in 7 US integrated and mixed-model health care systems and in Ontario, rates of CT and MRI use continued to increase among adults, but at a slower pace in more recent years. In children, imaging rates continued to increase except for CT, which stabilized or declined in more recent periods. Whether the observed imaging utilization was appropriate or was associated with improved patient outcomes is unknown.
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Corresponding Author: Rebecca Smith-Bindman, MD, Department of Radiology and Biomedical Imaging, Epidemiology and Biostatistics, University of California, San Francisco, 350 Parnassus Ave, Ste 307A, San Francisco, CA 94143 (email@example.com).
Accepted for Publication: July 24, 2019.
Author Contributions: Dr Miglioretti had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Smith-Bindman, Pole, Stout, Miglioretti.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Smith-Bindman.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Marlow, Cheng, Pole, Miglioretti.
Obtained funding: Smith-Bindman, Kwan, Miglioretti.
Administrative, technical, or material support: Smith-Bindman, Theis, Bolch, Bowles, Greenlee, Pole, Rahm, Weinmann.
Supervision: Smith-Bindman, Kwan, Bowles, Greenlee, Weinmann, Miglioretti.
Conflict of Interest Disclosures: Dr Duncan reported receipt of personal fees from Bayer. Dr Miglioretti reported previous advisory board membership for Hologic. No other disclosures were reported.
Funding/Support: This study was supported by the National Cancer Institute at the National Institutes of Health (grants R01CA185687 and R50CA211115). The Ontario portion of the study was also supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health, Long-Term Care. Parts of this material are based on data and/or information compiled and provided by the Canadian Institute for Health Information.
Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.
Additional Contributions: We acknowledge the contributions of the study team analysts: Glenn Buth, BAAS (Marshfield Clinic Health System), Melanie Francisco, PhD (KP Northwest), Giancarlo Di Giuseppe, MPH (Pediatric Oncology Group of Ontario), Stephanie Cheng, MSc (ICES), Matthew Lakota, MPH (Harvard Pilgrim Health Care), Dustin W. Ballard, BS (Geisinger), Joanne M. Mor, MS (KP Hawaii), and Kamala A. Deosaransingh, MPH (KP Northern California). We also acknowledge the contributions of the project coordinators/managers: Prachi Chavan, MPH (University of California, San Francisco), Charisma L. Jenkins, PSM (KP Northwest), Casey Luce, MSPH (KP Washington Health Research Institute), Deborah Multerer, BA (Marshfield Clinic Health System), Yannica S. Martinez, MS (KP Hawaii), Cindy Fong, BSc, CCRP (ICES), Julie R. Munneke, BA (KP Northern California), and Lisa M. Moy, MPH (KP Northern California). The above named contributors did not receive compensation outside of their regular employment pay.
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