Elsevier

Annals of Emergency Medicine

Volume 58, Issue 5, November 2011, Pages 452-462.e3
Annals of Emergency Medicine

Health policy/original research
National Trends in Use of Computed Tomography in the Emergency Department

https://doi.org/10.1016/j.annemergmed.2011.05.020Get rights and content

Study objective

The role of computed tomography (CT) in acute illnesses has increased substantially in recent years; however, little is known about how CT use in the emergency department (ED) has changed over time.

Methods

A retrospective study was performed with the 1996 to 2007 National Hospital Ambulatory Medical Care Survey, a large nationwide survey of ED services. We assessed changes during this period in CT use during an ED visit, CT use for specific ED presenting complaints, and disposition after CT use. Main outcomes were presented as adjusted risk ratios (RRs).

Results

Data from 368,680 patient visits during the 12-year period yielded results for an estimated 1.29 billion weighted ED encounters, among which an estimated 97.1 million (7.5%) patients received at least one CT. Overall, CT use during ED visits increased 330%, from 3.2% of encounters (95% confidence interval [CI] 2.9% to 3.6%) in 1996 to 13.9% (95% CI 12.8% to 14.9%) in 2007. Among the 20 most common complaints presenting to the ED, there was universal increase in CT use. Rates of growth were highest for abdominal pain (adjusted RR comparing 2007 to 1996=9.97; 95% CI 7.47 to 12.02), flank pain (adjusted RR 9.24; 95% CI 6.22 to 11.51), chest pain (adjusted RR 5.54; 95% CI 3.75 to 7.53), and shortness of breath (adjusted RR 5.28; 95% CI 2.76 to 8.34). In multivariable modeling, the likelihood of admission or transfer after a CT scan decreased over the years but has leveled off more recently (adjusted RR comparing admission or transfer after CT in 2007 to 1996=0.42; 95% CI 0.32 to 0.55).

Conclusion

CT use in the ED has increased significantly in recent years across a broad range of presenting complaints. The increase has been associated with a decline in admissions or transfers after CT use, although this effect has stabilized more recently.

Introduction

Use of computed tomography (CT) has increased dramatically across the US health care system during the past few decades, increasing more than 20-fold since 1980.1, 2 A substantial portion of this increase has been due to its expanding role in the diagnosis and early triage of patients with acute and sometimes life-threatening illnesses, including stroke,3 major trauma,4, 5, 6 head injury,7, 8, 9 pulmonary embolism,10, 11, 12 abdominal pain,13, 14, 15, 16 headache,17, 18, 19 renal colic,20, 21 and chest pain.22, 23, 24 As a result, some reports indicate that CT use in the emergency department (ED) may be increasing sharply relative to its use in other clinical settings.25, 26 In addition, one recent analysis has demonstrated increases in CT use in the ED for injuries, without a concurrent significant increase in the ability to diagnose major traumatic illness,27 whereas another has shown large increases in CT use at a single center.28

We are now beginning to understand how patterns of CT use in the ED have changed over time. However, little is known about how CT use has changed on a national scale over the range of common ED presenting conditions and, most important, whether changes in its use have been broad or limited to certain patients or clinical scenarios. We also do not know whether changes in CT use are associated with changes in ED disposition practices.

There are many potential concerns about the use of CT in the ED.29, 30, 31 These include its association with low-dose ionizing radiation exposure,32, 33, 34, 35, 36, 37 risks related to intravenous contrast exposure,38 and potential to discover incidental findings that require subsequent medical evaluations but may not improve outcomes.39, 40 Given these downsides, knowing which ED presenting complaints have experienced the largest increase in CT use might suggest areas of focus for future investigations into the benefits or disadvantages reaped by this change, as well as the potential need for evidence-based guidelines to better direct clinical practice. In addition, understanding the relationship between CT use and hospitalization decisionmaking, a major patient care outcome in the ED setting, has implications for policy and health care system costs.

Accordingly, we examined CT use in the ED during a recent 12-year period, using data from the National Hospital Ambulatory Medical Care Survey (NHAMCS), a large nationwide survey of ED services across the United States. We focused on describing overall patterns of CT use and change over time in key populations by patient demographics, visit characteristics, hospital factors, and presenting complaints. As a secondary analysis, we also explored how changes in CT use over the years of the study are associated with subsequent decisions to hospitalize or transfer to another facility.

Section snippets

Study Design, Setting, and Selection of Participants

We performed a retrospective cohort analysis of the ED component of NHAMCS for 1996 through 2007. NHAMCS is directed by the Centers for Disease Control and Prevention (CDC) and the National Center for Health Statistics. This survey, based on a complex survey design, collects a nationally representative sample of all ED visits in noninstitutional general and short-stay hospitals, excluding federal, military, and Veterans Administration hospitals. The institutional review board of the University

Characteristics of Study Subjects

The 1996 to 2007 NHAMCS data set included information on 368,680 ED visits sampled at 601 hospitals during the study period. These cases were weighted to represent an estimated 1,289,529,680 ED visits nationally during the study period. Table 2 displays CT use across various patient demographics, visit characteristics, and hospital factors. Because of the large size of the study population, statistically significant differences in all of these were observed between patients who underwent CT and

Limitations

Our study should be interpreted in the context of the following limitations. Given the nature of these data, we could not determine reasons CT was obtained for any individual patient. There may be important considerations that shape a decision to order a CT for a patient that involve medical, social, or economic factors. Another limitation is that our study addresses only disposition outcomes for an ED visit. It is not linked to patient outcomes beyond this period. Therefore, it is unknown

Discussion

We found substantial overall growth in CT use in US EDs between 1996 and 2007. During this period, ED visits increased by about 30%, whereas CT use increased 330%, meaning the rate of CT use increased to 11 times the ED visit rate. By 2007, approximately 1 in 7 patients with an ED visit underwent a CT scan as part of their evaluation. Given the large number of patients being treated annually in EDs, this finding has enormous implications for the general population. In fact, it suggests that

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    Please see page 453 for the Editor's Capsule Summary of this article.

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    Supervising editor: Ellen J. Weber, MD

    Author contributions: KEK was responsible for study concept and design, data acquisition, and statistical analysis; 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. All authors analyzed and interpreted the data and critically revised the article for important intellectual content. KEK and BKN drafted the article and supervised the study. KEK takes responsibility for the paper as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.

    Earn CME Credit: Continuing Medical Education is available for this article at: www.ACEP-EMedHome.com.

    Publication date: Available online August 11, 2011.

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