Dr. Chung and colleagues used two distinct data sets from CMS. First, they obtained annual Medicare Physician/Supplier Procedure Summary Master Files for 1994 to 2015. Aggregate counts for codes for chest radiography, CT, and ultrasound performed in the ED setting were extracted for each year. Given that Physician/Supplier Procedure Summary Master Files contain only aggregate national-level data, they also obtained CMS 5% research-identifiable files, which provide complementary individual service level information. These files are used to study geographic variation in the utilization of imaging services and were used to identify all individual claims for these same services in that 5% beneficiary sample, which were then aggregated to assess service level volumes for each state.
“Longitudinal state-by-state data revealed considerable heterogeneity in the extent of state-level increases of the use of thoracic imaging in the ED setting,” stated lead study author Jonathan Chung, MD, associate professor of radiology at The University of Chicago. “Despite this heterogeneity, nearly all individual states showed increased utilization over time for both ED thoracic radiology and CT.”
In Medicare beneficiaries, the use of noncardiac thoracic imaging in the ED setting grew markedly between this time period. This growth related not only to an increased frequency of ED visits but also to an increasing frequency of thoracic imaging per ED visit. Between 1994 and 2015, ED utilization of chest radiography and CT increased by 173% and 5,941.8%. Per 1,000 ED visits, utilization increased by 81% and 3,915.4%, respectively. Across states, utilization was highly variable, with 2015 radiography utilization per 1,000 ED visits ranging from 82 (Wyoming) to 731 (Hawaii) and CT utilization ranging from 18 (Wyoming) to 76 (Hawaii). Between 2004 and 2015, most states demonstrated increases in the utilization of both radiography and CT. Nonetheless, utilization of radiography declined in four states and utilization of CT in a single state.
“Over the past two decades, ED utilization of chest imaging has increased. This was related not only to an increasing frequency of ED visits but also to increasing utilization per ED visit,” added Andrew Rosenkrantz, MD, MPA, lead study author, professor and director of health policy in the department of radiology at NYU Langone Health and a Neiman Institute affiliate senior research fellow. “Across states, utilization is highly variable, but with radiography and CT both increasing, the use of CT seems additive to, rather than replacing, radiography.”
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