Value of computed tomography scans in ED dizziness visits: analysis from a nationally representative sample

Abstract

Objective

The study aimed to assess measures of the clinical value of computed tomography (CT) scans in dizziness presentations at the aggregate level.

Methods

Using emergency department (ED) dizziness presentations captured in the National Hospital Ambulatory Medical Care Survey, the proportion of dizziness visits with a CT scan that received a central nervous system (CNS) diagnosis was measured yearly (1995-2004) and assessed for a trend over time. The independent association of having a CT scan with ED length of stay was examined using multivariable linear regression models.

Results

The proportion of dizziness visits with a CT scan that received a CNS diagnosis dropped 62% from 1995 to 2004 (P < .05). By 2004, 94.1% (95% confidence interval, 89.4%-96.7%) of dizziness visits with a CT did not receive a CNS diagnosis. Having a CT scan was associated with a substantial increase in the length of stay with the effect modified by the number of other tests performed (range of increase, 40-77 minutes).

Conclusion

The clinical value of CT scans in dizziness presentations at the aggregate level may be very low and appears to have dropped over time. Computed tomography scans in the general dizziness population could also be an important contributor to ED length of stay. Use of CT scans in dizziness presentations should be a target for efforts to optimize the effectiveness and efficiency of care.

Introduction

When patients present with dizziness, physicians want to be confident that central nervous system (CNS) causes are “ruled out” [1], [2]. Although serious CNS causes of dizziness are uncommon [3], [4], [5], the consequences of misdiagnosis lower the testing threshold for brain imaging [6]. The most common type of brain imaging used in the acute setting is a computed tomography (CT) scan. A recent study found that the proportion of patients with dizziness presenting to the emergency department (ED) who undergo a CT scan increased from less than 10% in 1995 to more than 25% in 2004—a 169% increase in utilization [4].

However, the increasing use of CT as a diagnostic tool in dizziness presentations has major shortcomings because serious CNS causes are uncommon [3], [4], [5], the sensitivity of CT for ischemic stroke—the typical target disorder of the test—is very low [7], [8], [9], “silent” or incidental findings are common [10], [11], and the test is expensive. In addition, having a CT scan may increase the ED length of stay [12], [13]. These shortcomings may adversely impact the clinical value (ie, usefulness) of the test because the value of a test is largely dependent on the prevalence (or the clinician's estimate of the pretest probability) of the target disorder, the accuracy of the test for the target disorder, and the relative benefit-to-harm ratio [14]. A CT scan is a highly accurate test for intracranial hemorrhage [7], but intracranial hemorrhage is a very unlikely cause in a general dizziness sample [3], [4]. Defining the value of tests in clinical care is a goal of health care reform efforts because use of tests contributes to cost and quality of care.

In the current study, we aim to measure some other factors related to CT use in dizziness presentations that might help to estimate the value of CT scans when considered at the aggregate level. Specifically, we aim to measure the yield of CT scans for CNS diagnoses, to test for a trend in yield over time, and to measure the effect of CT scans on ED length of stay using a nationally representative sample.