U.S. Trends in Computed Tomography Use and Diagnoses in Emergency Department Visits by Patients With Symptoms Suggestive of Pulmonary Embolism, 2001–2009

Diagnosing pulmonary embolism (PE) in emergency department (ED) patients is challenging because the cardiopulmonary symptoms common to PE can mimic other clinical entities such as pneumonia, respiratory conditions such as asthma, and nonrespiratory conditions such as acute coronary syndrome.1 D-dimer assays are highly sensitive but poorly specific initial tests for low-risk PE patients and may reduce the need for computed tomography (CT) pulmonary angiography; however, this is not always the case in practice.2,3 Some physicians rely on CT as an initial test in cases of suspected PE. In addition, testing very low-risk patients with nonspecific D-dimer assays can lead to high rates of false-positive D-dimers, and ultimately negative CT scans. CT is the test of choice to diagnose PE in the ED, but overuse of CT is a concern because it can be associated with a small number of serious adverse events such as contrast-induced nephropathy, reactions to intravenous contrast dye, and radiation-induced cancer.4–13 Rates of CT use in U.S. EDs have risen dramatically over the past two decades, from 2.7 million in 1995 to 16.2 million in 2007.10,14–17 A similar rise has been observed in ED patients with chest pain: in 1995, 1.2% received CTs; the rate increased to 13.7% by 2007.14 Previous chart-based studies also reported up to 13-fold increases in use of PE-protocol CT scans over several years.18,19 The benefits of the observed proliferation of CTs on PE care is mixed, however. One study of U.S. EDs found that increases in PE diagnoses did not coincide with increases in CT use, comparing 1997 through 1999 to 2005 through 2007.20 “Overdiagnosis” is also a concern, as there is evidence of increased diagnosis of low-risk or asymptomatic PE, while absolute deaths have remained the same, resulting in a diminishing case fatality rate for PE.21,22 Most recently, the American College of Physicians included CT use as an initial test for patients at low risk for PE on a list of low-value practices that should be discouraged.23 Thorough understanding of these issues is critical during this period of health reform, as the nation is looking for ways to cut costs, reduce waste, and improve quality. In this study, we explored longitudinal trends in the use of CT scans in U.S. EDs for three PE-related symptoms (chest pain, dyspnea, and hemoptysis) from 2001 through 2009 using a nationally representative sample: the National Hospital Ambulatory Care Survey. Recent studies have explored increases in CT use using national data, but our study is novel in several ways. First, we analyzed national trends in ED CT use beyond 2007, using data from 2008 and 2009. Second, we assessed the proportion of visits with PE diagnoses where CT may have contributed to the diagnostic process; for this we estimated the ratio of the number of visits with CTs and diagnoses, relative to the number of visits with CTs in our chest symptom study (CSS) group (diagnosis/CT ratio). This allowed us to compare the ratio for PE—a diagnosis that is usually sought on CT scans—with pneumonia, a diagnosis that can be captured on plain radiography but is sometimes found on CT in a search for suspected PE.24