AJR AJR-based Continuing Ed for Technologists
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ladapo, J. A.
Right arrow Articles by Gazelle, G. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ladapo, J. A.
Right arrow Articles by Gazelle, G. S.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?
Hotlight (NEW!)
Right arrow
What's Hotlight?
DOI:10.2214/AJR.07.3611
AJR 2008; 191:455-463
© American Roentgen Ray Society

Original Research

Cost-Effectiveness of Coronary MDCT in the Triage of Patients with Acute Chest Pain

Joseph A. Ladapo1, Udo Hoffmann2,3, Fabian Bamberg2, John T. Nagurney4, David M. Cutler5,6, Milton C. Weinstein7 and G. Scott Gazelle2,3,7,8

1 Harvard Ph.D. Program in Health Policy, 14 Story St., 4th Floor, Cambridge, MA 02138.
2 Department of Radiology, Massachusetts General Hospital, Boston, MA.
3 Harvard Medical School, Boston, MA.
4 Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA.
5 Department of Economics, Harvard University, Cambridge, MA.
6 National Bureau of Economic Research, Cambridge, MA.
7 Department of Health Policy and Management, Harvard School of Public Health, Boston, MA.
8 Institute for Technology Assessment, Massachusetts General Hospital, Boston, MA.

Received January 1, 2008; accepted after revision March 4, 2008.

 
Funding for this study was provided through the Walker Fund of the Harvard Ph.D. Program in Health Policy, which provided support for the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation and review of the manuscript. Any errors or omissions are the sole responsibility of the authors. Joseph A. Ladapo had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Address correspondence to J. A. Ladapo (joseph.ladapo{at}gmail.com).


Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
OBJECTIVE. Patients at low risk for acute coronary syndrome (ACS) who present to the emergency department complaining of acute chest pain place a substantial economic burden on the U.S. health care system. Noninvasive 64-MDCT coronary angiography may facilitate their triage, and we evaluated its cost-effectiveness.

MATERIALS AND METHODS. A microsimulation model was developed to compare costs and health effects of performing CT coronary angiography and either discharging, stress testing, or referring emergency department patients for invasive coronary angiography, depending on their severity of atherosclerosis, compared with a standard-of-care (SOC) algorithm that based management on biomarkers and stress tests alone.

RESULTS. Using CT coronary angiography to triage 55-year-old men with acute chest pain increased emergency department and hospital costs by $110 and raised total health care costs by $200. In 55-year-old women, the technology was cost-saving; emergency department and hospital costs decreased by $410, and total health care costs decreased by $380. Compared with the SOC, CT coronary angiography-based triage extended life expectancy by 10 days in men and by 6 days in women. This translated into corresponding improvements of 0.03 quality-adjusted life years (QALYs) and 0.01 QALYs, respectively. The incremental cost-effectiveness ratio for CT coronary angiography was $6,400 per QALY in men; in women, CT coronary angiography was cost-saving. Cost-effectiveness ratios were sensitive to several parameters but generally remained in the range of what is typically considered cost-effective.

CONCLUSION. CT coronary angiography-based triage for patients with low-risk chest pain is modestly more effective than the SOC. It is also cost-saving in women and associated with low cost-effectiveness ratios in men.

Keywords: acute chest pain • cardiac CT • cost-effectiveness • health policy • noninvasive angiography


Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Patients who present to the emergency department complaining of acute chest pain place a substantial economic burden on the U.S. health care system. In 2004 alone, more than 6 million such visits occurred, and an estimated 30% of them resulted in hospitalization for suspected acute coronary syndrome (ACS), a condition that includes myocardial infarction (MI) and unstable angina [1, 2]. Although some of the many patients who are admitted because of these suspicions are ultimately diagnosed with ACS, many are not, and inpatient care for negative evaluations is estimated to cost several billion dollars annually [3].

Patients who are at low risk for ACS because of negative initial cardiac biomarkers and normal or nondiagnostic ECG examinations, but in whom the source of chest pain is not readily identified, are a cohort whose management is notably inefficient [4–7]. The American College of Cardiology (ACC) and the American Heart Association (AHA) recommend further evaluation for these patients, but their hospitalizations typically result in benign diagnoses [5, 8, 9].

Because ACS is rare in the absence of coronary atherosclerotic plaque, several researchers have suggested that the incorporation of noninvasive CT coronary angiography may improve the triage of patients with acute chest pain and reduce health care costs [3, 10–14]. Many of these researchers have based their proposals on the capabilities of the relatively new 64-MDCT.

High spatial and temporal resolution is offered by 64-MDCT, which generates diagnostically useful images of the coronary artery lumen and wall [15]. Because these vessels are the site of atherosclerotic plaques that lead to ACS, 64-MDCT coronary angiography (CT coronary angiography), by excluding the presence of atherosclerosis, may facilitate the triage of patients with acute chest pain who are suspected of having ACS.

Our review of the literature identified a small but growing number of studies examining the usefulness of 64-MDCT in a clinical setting. In a prospective observational cohort study, Hoffmann et al. [10] found that 64-MDCT coronary angiography accurately distinguished a subset of patients with chest pain who could be safely sent home from the emergency department. Rubinshtein et al. [16] incorporated CT coronary angiography in a similar patient population and concluded that MDCT identified the presence of ACS with high sensitivity and was also moderately specific. Gallagher et al. [3] reached similar conclusions. Nonetheless, except for a small but novel randomized controlled trial conducted by Goldstein et al. [14], little is known about the impact of CT coronary angiography on health care costs, and larger studies evaluating its effectiveness in comparison with traditional triage strategies are still in their early stages. In the absence of this information, an economic evaluation of CT coronary angiography is warranted to help guide hospitals and policy makers who are considering acquiring 64-MDCT and reimbursing their use in an emergent chest pain setting. We constructed an analytic model to aid these policy makers in their decisions.


Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Simulation Model
We developed a Monte Carlo microsimulation model to compare the standard of care (SOC) with CT coronary angiography-based management in the triage of patients with low-risk chest pain who present to the emergency department [17]. In the SOC pathway, patients are evaluated with a stress test and admitted for invasive coronary angiography if their results are abnormal. In the CT coronary angiography pathway, patients are imaged and either discharged, evaluated with a stress test, or sent directly to invasive coronary angiography, depending on the severity of their atherosclerosis. Detailed descriptions of the two pathways are provided in a later section. The primary outcomes measured were longevity (in quality-adjusted life years [QALYs]), health care costs related to emergency department visits for acute chest pain, the number of hospital admissions averted, and the rate of missed cases of ACS. Costs were reported in 2005 U.S. dollars; we used a 3% discount rate on costs and QALYs and adopted a societal perspective [18].

Population Characteristics
We conducted separate analyses for 55-year-old men and women with "low-risk chest pain," defined as patients with negative initial troponin measurements, a normal or nondiagnostic ECG, and no history of heart disease. We did not include patients with very low-risk chest pain, who would be discharged without cardiac evaluation, or patients with ST segment elevation MIs. The diagnosis of coronary artery disease (CAD) was reserved for patients with significant coronary disease, defined by either ≥ 50% stenosis in the left main coronary artery or ≥ 70% stenosis in any other coronary artery. Patients whose atherosclerosis did not meet the definition for CAD were considered to have "early heart disease" or mild stenosis, and those with no atherosclerosis were considered healthy.

Overview of Model and Triage Strategies
Patients begin the model in the emergency department with acute chest pain, negative initial biomarkers, a normal or nondiagnostic ECG, and no history of heart disease. Chest pain is either ACS (with non-ST segment elevation MI or unstable angina) or non-ACS (chronic stable angina or noncardiac chest pain) in origin. Subsequent management loosely follows an algorithm proposed by Goldstein et al. [14] in their randomized controlled trial of CT coronary angiography in the emergency department.

In the SOC pathway, patients are assumed to still have normal or nondiagnostic ECGs and await the results of their final troponin measurement. They are evaluated with a stress test if the enzyme is not found to be elevated (Fig. 1). Patients with elevated follow-up biomarkers or whose stress tests confirm ischemia are referred for invasive coronary angiography. Coronary catheterization is followed by percutaneous coronary intervention (for one- or two-vessel disease) or coronary artery bypass graft (CABG) surgery (for left main and three-vessel disease) if their angiograms reveal significant stenosis. Mild coronary stenosis is managed medically. If the stress test and follow-up troponin measurement are normal in the emergency department, patients are eligible for discharge.


Figure 1
View larger version (5K):
[in this window]
[in a new window]
[as a PowerPoint slide]
  		Fig. 1 —Decision pathway for patients with low-risk chest pain presenting to emergency department and managed under standard-of-care algorithm. CABG = coronary artery bypass graft, Cath + = coronary catheterization reveals significant stenosis, Cath – = coronary catheterization reveals mild or no stenosis, LM = left main artery disease, n-v = n-vessel disease, PCI = percutaneous coronary intervention, Trop/Stress test + = troponin elevated or stress test positive for ischemia, Trop/Stress test – = troponin normal and stress test negative for ischemia.

 

In the CT coronary angiography care pathway, patients are imaged, and those with evidence of normal coronary arteries are discharged from the emergency department with no further testing (Fig. 2). Patients with mild atherosclerotic lesions are evaluated with follow-up biomarker measurements and stress tests, as in the SOC algorithm. Further management also follows the SOC pathway, and patients may be discharged if their examinations are normal or if they are referred for coronary catheterization. Patients with evidence of significant stenosis on CT coronary angiography are also referred for coronary catheterization.


Figure 2
View larger version (8K):
[in this window]
[in a new window]
[as a PowerPoint slide]
  		Fig. 2 —Decision pathway for patients with low-risk chest pain presenting to emergency department and managed under CT coronary angiography algorithm. CABG = coronary artery bypass graft, Cath + = coronary catheterization reveals significant stenosis, Cath – = coronary catheterization reveals mild or no stenosis, CTCA ++ = CT coronary angiography positive for significant stenosis, CTCA + = CT coronary angiography positive for mild stenosis, CTCA – = CT coronary angiography negative for any atherosclerosis, LM = left main artery disease, n-v = n-vessel disease, PCI = percutaneous coronary intervention, Trop/Stress test + = troponin elevated or stress test positive for ischemia, Trop/Stress test – = troponin normal and stress test negative for ischemia.

 
After being discharged from the emergency department or inpatient hospital service, patients return to a baseline state of health, in which health risks are determined by age, sex, ACS history, atherosclerotic status, and cardiac health interventions. They also accrue health care costs related to emergency department care, inpatient hospitalization, and cardiac medications and interventions. Over the course of their lives, patients may potentially progress from a healthy status to early heart disease, undiagnosed CAD, diagnosed CAD, and death. Patients who are not diagnosed with CAD in the emergency department and do not transition from undiagnosed to diagnosed CAD may return to the emergency department for acute chest pain episodes that fit a low-risk profile, for which the annual risk of an emergency department revisit was assumed to be 20% for each of the next 5 years [19, 20] (Fig. 3).


Figure 3
View larger version (12K):
[in this window]
[in a new window]
[as a PowerPoint slide]
  		Fig. 3 —Health states for patients with chest pain. CAD = coronary artery disease.

 

Distribution of Disease in Patients with Acute Chest Pain
The distribution of ACS and non-ACS diagnoses in the initial emergency department visit was primarily derived from a study of 317 patients with acute chest pain who had no history of heart disease and were considered to be at low risk for ACS on the basis of a clinical algorithm constructed by Goldman et al. [21, 22] and other authors [9, 23]. Data from a study of 817 emergency department patients with chest pain were also used [24]. Low-risk patients with non-ACS chest pain were assumed not to have a life-threatening condition (Table 1). Although this is not true in reality, because such patients may be experiencing aortic dissections, pulmonary embolisms, or other conditions, our omission of any explicit modeling of these health events likely does not affect incremental cost-effectiveness because these patients are presumably evaluated similarly under both management strategies.


View this table:
[in this window]
[in a new window]

  		TABLE 1: Patient and Diagnostic Test Characteristics

 

After the initial chest pain episode, the distribution of disease in subsequent emergency department visits was estimated using simplifying assumptions and bayesian methods. For example, a patient with CAD who returned to the emergency department with chest pain would have a probability of experiencing non-ST segment elevation MI equal to (0.8) (0.03) / [(0.8) (0.03) + (0.5) (0.97)], where 0.8, 0.03, 0.5, and 0.97 are, respectively, the probabilities, in the initial emergency department visit, of a patient having CAD conditional on experiencing non-ST segment elevation MI, the total probability of a patient experiencing non-ST segment elevation MI, the probability of a patient having CAD conditional on experiencing non-ST segment elevation MI chest pain, and the total probability of a patient experiencing non-ST segment elevation MI chest pain. In this example, the 0.8 and 0.5 figures are fictitious (the actual values vary by sex), and we have collapsed the conditional probabilities of CAD in the presence of unstable angina, stable angina, and noncardiac chest pain for illustrative purposes.

Prevalence of Atherosclerosis
The distribution of coronary atherosclerosis among patients with acute chest pain is critical to the effectiveness of 64-MDCT as a triage and diagnostic instrument. We derived this distribution from a large cohort of patients with chest pain who underwent invasive angiography but were not diagnosed with ACS [25]. These patients were stratified by age, sex, and the likelihood that their chest pain complaints were anginal in nature (definite angina, probable angina, or nonspecific chest pain).

Patients with ACS were assigned a distribution of vessel disease similar to the "definite angina" chest pain group; patients with stable angina were assigned a distribution of vessel disease that averaged results from the definite angina and probable angina groups because we assumed these patients were healthier than patients with ACS; patients with noncardiac chest pain were assigned a distribution of vessel disease similar to the nonspecific chest pain group. Because patients in this group are unlikely to be experiencing cardiac chest pain, their vessel disease distribution was assumed to be representative of a random sample of U.S. adults. Note that our method of estimating vessel disease patterns permits the occurrence of ACS in the absence of significant atherosclerosis, a phenomenon that has been previously documented [26–28].

Diagnostic Tests and Procedures
No published studies have reported all 64-MDCT coronary angiography test characteristics needed for our model on a per-patient basis, so we used data that applied to individual segments of the coronary arteries [29] (Table 1). Note that this method of reporting will, on average, underestimate the diagnostic power of CT coronary angiography because many patients have multiple significant coronary lesions. The diagnostic performance of other tests, including serial troponin measurements, stress ECG, stress echocardiography, and SPECT myocardial perfusion imaging (SPECT MPI), for identifying ACS or CAD (in patients without ACS but with CAD) was derived from a meta-analysis [30]. We assumed that patients were equally likely to undergo evaluation with any of these stress test techniques. Coronary CT angiography yielded nondiagnostic results at a rate of 4%, and patients with nondiagnostic examinations were subsequently evaluated with a stress test [31]. The risks and benefits of CABG and percutaneous coronary intervention were derived from a previous decision analysis [32].

Long-Term Survival
Mortality risk over time was based on age, sex, the existence and severity of CAD, history of CABG or percutaneous coronary interventional treatment, and history of ACS [26, 32–34] (Table 2). Patients wrongfully discharged from the emergency department with undiagnosed ACS faced an elevated risk of mortality [35]. The likelihood of developing atherosclerosis was estimated using data from a previous study, and the annual probability of transitioning from undiagnosed to diagnosed CAD was assumed to be 5% [25].


View this table:
[in this window]
[in a new window]

  		TABLE 2: Mortality Risks for Disease Conditions and Procedures

 

Health-Related Quality of Life
CAD may be associated with chronic chest discomfort; therefore, health-related quality of life in this study was based on the existence and severity of this discomfort. Utilities for various chest discomfort classifications were derived from a study of 878 Canadian patients using the standard gamble method and were combined with data on the impact of CABG and percutaneous coronary intervention on chest pain [36, 37] (Table 3).


View this table:
[in this window]
[in a new window]

  		TABLE 3: Utilities and Resource Utilization for Patients with Acute Chest Pain

 

Health Care Costs
Emergency department and inpatient costs were estimated using data from a randomized controlled trial reported by Goldstein et al. [14] and Medicare reimbursement data [38] (Table 3). Using the former, we derived the implicit cost of care for patients discharged from the emergency department and adjusted this cost using national Medicare reimbursement rates for stress SPECT examinations. We then used the difference between the reported cost of stress SPECT in the randomized controlled trial and the average national Medicare reimbursement for this examination to estimate the cost of CT coronary angiography. Note that Medicare's fee schedule is considered a reasonable proxy for economic costs [39]. The annual cost of medications for CAD and angina was estimated using assumptions about typical treatment doses for statins, aspirin, β-blockers, and isosorbide mononitrate.

Model Analysis
We ran 1,000,000 first-order Monte Carlo microsimulations for 55-year-old men and women and performed one-way sensitivity analyses on key parameters. The model was built with TreeAge Pro Suite 2006 (TreeAge Software), and results were analyzed using Excel 2003 (Microsoft) and Intercooled Stata 9.2 software (Stata).


Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Base Case Analysis
Using CT coronary angiography to triage men with acute chest pain increased emergency department and hospital costs by $110 and raised total health care expenditures by $200 (Table 4). In women, the technology was cost-saving, and emergency department and hospital costs decreased by $410; total health care expenditures decreased by $380. These figures represent a balance between the cost increases associated with earlier detection and treatment of CAD because the test characteristics of CT coronary angiography are superior to conventional diagnostic techniques and because of the cost savings from the emergency department discharge of patients unlikely to be experiencing ACS. Indeed, 97% of men and women with unknown CAD were diagnosed in the first emergency department visit, compared with 85% under the SOC strategy, and emergency department discharge rates were also higher.


View this table:
[in this window]
[in a new window]

  		TABLE 4: Costs, Health Outcomes, and Cost-Effectiveness of Triage Strategies for Patients with Acute Chest Pain

 

Both sexes experienced incremental improvements in unadjusted and quality-adjusted life expectancy (QALE) with CT coronary angiography, but the benefits were small. Compared with the SOC, CT coronary angiography-based triage extended life expectancy by 10 days in men and 6 days in women (Table 4). This translated into corresponding improvements of 0.03 and 0.01 QALYs, respectively. The modest improvements reflect the low incidence of ACS in our cohort. Compared with the SOC, the incremental cost-effectiveness ratio for CT coronary angiography management was $6,400 per QALY in men; in women, the strategy was cost-saving (Table 4).

Emergency department discharge rates in men and women were 69% and 82% in the MDCT algorithm and 62% and 65% in the SOC algorithm, respectively. These discharges were associated with a rate of missed ACS of 1% in men under both management algorithms. In women, the missed ACS rate was 1% under SOC management and 2% under CT coronary angiography management. Whereas only 13% of these missed cases occurred in the setting of cardiac syndrome X under SOC management, this figure approached 80% in men evaluated with CT coronary angiography. The corresponding percentages in women were 48% and 95%. Thus, most patients who were wrongfully discharged from the emergency department after being triaged with CT coronary angiography (with or without stress testing) faced a low risk of mortality from the missed diagnosis [40].

Sensitivity Analysis
We conducted sensitivity analyses using the data ranges specified in Tables 1, 2, 3. In general, varying key parameters over plausible ranges changed incremental cost-effectiveness ratios but left CT coronary angiography-based triage as the preferred strategy when compared with the SOC.

Reducing by 25% the ability of CT coronary angiography to correctly classify a healthy patient as having normal coronary arteries increased its incremental cost-effectiveness ratio to $17,000 per QALY in men but made little difference in women. Minimizing the ability of CT coronary angiography to classify a patient with CAD as having significant stenosis marginally affected its cost-effectiveness in men, but CT coronary angiography remained a cost-saving strategy in women compared with the SOC. The QALY benefit also decreased modestly in men, primarily because fewer patients were diagnosed with CAD and treated. Reducing the time horizon over which patients could return to the emergency department to 1 year increased the incremental cost-effectiveness ratio of CT coronary angiography-based management to $15,000 per QALY in men, but this strategy remained cost-saving in women. The difference in total health care expenditures between SOC and CT coronary angiography-based management rose to $530 in men, and cost savings in women decreased to $80 in women.

Increasing the prevalence of nondiagnostic CT coronary angiography examinations to 10% also had little quantitative impact on the results. Maximizing the 30-day mortality risk associated with missed ACS widened the gap between QALY outcomes in the two strategies, and the incremental cost-effectiveness ratio in men decreased to $4,040 per QALY. Increasing the cost of CT coronary angiography to $1,000 per examination increased the incremental cost-effectiveness of CT coronary angiography to $25,300 per QALY in men and disrupted the cost-saving relationship between the two strategies in women (Fig. 4). The incremental cost-effectiveness of CT coronary angiography was $17,200 per QALY in this population.


Figure 4
View larger version (9K):
[in this window]
[in a new window]
[as a PowerPoint slide]
  		Fig. 4 —Incremental cost-effectiveness of CT coronary angiography (CTCA) management at varying examination costs for men (solid line) and women (dashed line). QALY = quality-adjusted life year.

 
We also assessed the impact of evaluating patients with only one type of stress test instead of randomly allocating them to either stress SPECT, stress echocardiography, or ECG. Note that this change was made in both the SOC and CT coronary angiography arms simultaneously. When all patients undergoing stress tests were studied with stress SPECT, CT coronary angiography-based triage reduced overall costs and increased QALYs in both sexes, making the strategy cost-saving for men and women. When all patients were studied with stress echocardiography, CT coronary angiography-based triage raised overall costs in men and reduced them in women but continued to improve health outcomes in both sexes. The cost-effectiveness of CT coronary angiography rose to $15,500 per QALY in men. Evaluating all patients with stress ECG yielded similar results as the analysis of stress echocardiography, and the cost-effectiveness of CT coronary angiography was $15,700 in men, whereas the strategy remained cost-saving in women.


Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Our findings suggest that CT coronary angiography-based triage for patients with low-risk chest pain yields slightly higher health care costs in men and lower costs in women, may be modestly more effective than the SOC in prolonging life and QALYs, and is associated with low cost-effectiveness ratios in men and cost savings in women. In men, cost-effectiveness ratios remain within the range of what is typically considered to be cost-effective, even when several parameters are varied. In women, CT coronary angiography is cost-saving under a wide variety of model assumptions. We also found that both CT coronary angiography and the SOC are associated with a low rate of missed ACS, and that the portion of these cases that represent incidences of cardiac syndrome X is much higher with CT coronary angiography. This incidence is higher because, under the SOC, nearly all syndrome X patients are admitted, whereas CT coronary angiography-based triage will generally lead to their discharge because most will have negative imaging tests.

CT coronary angiography raised overall costs in men primarily because it was more likely to identify patients with CAD. These patients incurred costs related to a lifetime of cardiovascular treatment. However, they also gained risk reductions because of this treatment. Thus, though overall costs were higher, QALYs also rose, and this combination yielded a low (favorable) cost-effectiveness ratio. In contrast, CT coronary angiography lowered overall costs in women because savings from avoided admissions outweighed cost increases from a higher rate of detection and treatment of CAD. The balance swung in favor of cost savings in women because the prevalence of CAD in this population is relatively low, whereas in men, the costs rose because their CAD prevalence is relatively high. CT coronary angiography increased QALYs in women through a similar mechanism as it did in men, but it also did so by shielding appropriately discharged patients from the risks of diagnostic testing, particularly cardiac catheterization. Thus, no incremental cost-effectiveness ratio was calculated for women, and CT coronary angiography was deemed cost-saving.

The results of our analysis generally meet our a priori expectations of the impact of CT coronary angiography on costs and health outcomes: A technology with its diagnostic characteristics would be expected to be cost-saving in populations with suspected ACS but a low prevalence of CAD. In populations with a higher prevalence of CAD, we believe the net impact of CT coronary angiography is more difficult to predict: Admissions might increase because of the test's sensitivity, raising costs but potentially improving health outcomes, or costs could fall because of savings from emergency department discharges.

In future studies, we hope researchers will analyze the cost-effectiveness of CT coronary angiography in the context of other management algorithms. For example, although we referred patients with mild stenosis on CT coronary angiography for stress testing, these patients could plausibly be discharged. Managing them in this manner may have significant health and economic consequences. Similarly, although we assumed that patients undergoing stress tests were equally likely to undergo stress ECG, stress echocardiography, or SPECT, the choice of diagnostic test could be better tailored to a patient's demographic and clinical characteristics. As one recent review of nuclear imaging suggests, the primary test choice for some patients may be CT coronary angiography, with or without SPECT, whereas other patients may benefit more from the anatomic and functional information gleaned from cardiac MRI [41]. These patient-tailored algorithms could be incorporated into a decision tree.

Emergency department, hospital, and total health expenditures, along with the estimated effectiveness of the two management strategies, were sensitive to several parameters, including the rate at which patients with low-risk chest pain returned to the emergency department, the test characteristics of 64-MDCT, and the cost of CT coronary angiography. Nonetheless, 64-MDCT coronary angiography-based triage was generally still associated with improved health benefits in both sexes and cost savings in women when compared with the SOC.

Our results may not be generalizable to other countries, where the demographics and epidemiology of CAD vary and the economic value of resources used in care also differ [42, 43]. Furthermore, in the United States, the generalizability of our results may be limited to regions in which disease distribution, clinical practices, and economic costs are similar to those we evaluated. However, the sensitivity analyses suggest that our results are applicable under many different conditions.

Our study has several limitations. We modeled a clinical situation in which the population of interest has several key unknowns, including the distribution of diagnoses and the extent of arterial disease. Because of the lack of data in this area, we assumed age- and sex-independent distributions of diagnoses for different demographic groups and ascribed vessel disease distributions using a parallel patient population. Data on these parameters would have improved the analysis but were not available in the literature. We also did not incorporate information on whether patients had a history of diabetes, hypertension, hypercholesterolemia, or smoking for similar reasons. These inputs would have made our study more robust.

We also assumed that patients with noncardiac chest pain did not face an increased risk of death from being discharged instead of hospitalized. Although they may theoretically be suffering from a multitude of fatal conditions, including pulmonary embolism, esophageal rupture, and other conditions, we assumed that these patients could be differentiated from patients who can safely be followed up in a primary care setting.

Also, we did not consider the economic or health impact of incidental findings discovered on CT coronary angiography. These findings would almost certainly increase the costs associated with CT coronary angiography-based strategies for triaging patients with acute chest pain but may also be associated with improved longevity, depending on the distribution of undiagnosed conditions in that population. This is an important area of uncertainty that warrants further investigation.

Finally, in the randomized controlled trial conducted by Goldstein et al. [14], patients with mild coronary atherosclerosis (< 25% stenosis) on CT coronary angiography were discharged, whereas we submitted these patients to stress testing in our model. This difference highlights the general issue of differential interpretation and application of test results, and the impact of MDCT on patient outcomes is likely to be sensitive to the treatment thresholds applied by clinicians.

Related to this issue are the implications of CT coronary angiography for patient resource utilization in the outpatient setting. Negative CT coronary angiography examinations may provide clinicians and patients with reassurance and extinguish any intentions of performing further CAD diagnostic studies in an outpatient setting. In contrast, some CT coronary angiography examinations will identify incidental findings that may require regular follow-up long after the patient is discharged from the hospital. We conjecture that the overall impact of CT coronary angiography on outpatient resource utilization is ambiguous and will require further investigation.

Despite these limitations, our results suggest that 64-MDCT coronary angiography may be a safe addition to the management of low-risk patients with acute chest pain and is likely to be cost-saving in women and marginally more expensive than the SOC in men. Its high sensitivity for coronary atherosclerosis compared with conventional diagnostic technologies may also hasten the identification and treatment of CAD in patients with an unknown history of CAD. Clinical trials evaluating this technology are under way and may ultimately illuminate a more efficient and cost-effective management approach to low-risk patients with chest pain in the emergency department.


Acknowledgments
 
We thank Claudia Chae for her helpful comments on the structure of the simulation model.


References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. McCaig LF, Nawar EW. National Hospital Ambulatory Medical Care Survey: 2004 emergency department summary. Adv Data2006; 372:1 -29[Medline]
  2. Gibler WB, Cannon CP, Blomkalns AL, et al. Practical implementation of the Guidelines for Unstable Angina/Non-ST-Segment Elevation Myocardial Infarction in the emergency department. Ann Emerg Med2005; 46:185 -197[CrossRef][Medline]
  3. Gallagher MJ, Ross MA, Raff GL, Goldstein JA, O'Neill WW, O'Neil B. The diagnostic accuracy of 64-slice computed tomography coronary angiography compared with stress nuclear imaging in emergency department low-risk chest pain patients. Ann Emerg Med 2007;49 : 125-136[CrossRef][Medline]
  4. Hillis GS, Oliner C, O'Neil BJ, et al. Coronary artery disease in patients with chest pain who have low-risk clinical characteristics and negative cardiac troponin I. Am J Emerg Med2001; 19:118 -121[CrossRef][Medline]
  5. Buchsbaum M, Marshall E, Levine B, et al. Emergency department evaluation of chest pain using exercise stress echocardiography. Acad Emerg Med 2001;8 : 196-199[Medline]
  6. Amsterdam EA, Lewis WR, Yadlapalli S. Evaluation of low-risk patients with chest pain in the emergency department: value and limitations of recent methods. Cardiol Rev 1999;7 : 17-26[Medline]
  7. Lee TH, Goldman L. Evaluation of the patient with acute chest pain. N Engl J Med 2000;342 : 1187-1195[Free Full Text]
  8. Braunwald E, Antman EM, Beasley JW, et al. ACC/AHA 2002 guideline update for the management of patients with unstable angina and non-ST-segment elevation MI: summary article—a report of the American College of Cardiology/American Heart Association task force on practice guidelines (Committee on the Management of Patients With Unstable Angina). J Am Coll Cardiol 2002; 40:1366 -1374[Free Full Text]
  9. Zalenski RJ, McCarren M, Roberts R, et al. An evaluation of a chest pain diagnostic protocol to exclude acute cardiac ischemia in the emergency department. Arch Intern Med 1997;157 : 1085-1091[Abstract/Free Full Text]
  10. Hoffmann U, Nagurney JT, Moselewski F, et al. Coronary multidetector computed tomography in the assessment of patients with acute chest pain. Circulation 2006;114 : 2251-2260[Abstract/Free Full Text]
  11. Hoffmann U, Pena AJ, Moselewski F, et al. MDCT in early triage of patients with acute chest pain. AJR 2006;187 : 1240-1247[Abstract/Free Full Text]
  12. Schroeder S, Kuettner A, Beck T, et al. Usefulness of noninvasive MSCT coronary angiography as first-line imaging technique in patients with chest pain: initial clinical experience. Int J Cardiol2005; 102:469 -475[CrossRef][Medline]
  13. Raff GL, Gallagher MJ, O'Neill WW, Goldstein JA. Diagnostic accuracy of noninvasive coronary angiography using 64-slice spiral computed tomography. J Am Coll Cardiol 2005;46 : 552-557[Abstract/Free Full Text]
  14. Goldstein JA, Gallagher MJ, O'Neill WW, Ross MA, O'Neil BJ, Raff GL. A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain. J Am Coll Cardiol2007; 49:863 -871[Abstract/Free Full Text]
  15. Hoffmann U, Ferencik M, Cury RC, Pena AJ. Coronary CT angiography. J Nucl Med 2006;47 : 797-806[Abstract/Free Full Text]
  16. Rubinshtein R, Halon DA, Gaspar T, et al. Usefulness of 64-slice cardiac computed tomographic angiography for diagnosing acute coronary syndromes and predicting clinical outcome in emergency department patients with chest pain of uncertain origin. Circulation2007; 115:1762 -1768[Abstract/Free Full Text]
  17. Kuntz KM, Weinstein MC. Modeling in economic evaluation. In: Drummond M, McGuire A, eds. Economic evaluation in health care: merging theory with practice. New York, NY: Oxford University Press, 2001: 150-152
  18. Gold MR, Siegel JE, Russell LB, Weinstein MC, eds. Cost-effectiveness in health and medicine. New York, NY: Oxford University Press, 1996
  19. deFilippi CR, Rosanio S, Tocchi M, et al. Randomized comparison of a strategy of predischarge coronary angiography versus exercise testing in low-risk patients in a chest pain unit: in-hospital and long-term outcomes. J Am Coll Cardiol 2001;37 : 2042-2049[Abstract/Free Full Text]
  20. Polanczyk CA, Johnson PA, Hartley LH, Walls RM, Shaykevich S, Lee TH. Clinical correlates and prognostic significance of early negative exercise tolerance test in patients with acute chest pain seen in the hospital emergency department. Am J Cardiol 1998;81 : 288-292[CrossRef][Medline]
  21. Goldman L, Cook EF, Brand DA, et al. A computer protocol to predict MI in emergency department patients with chest pain. N Engl J Med 1988; 318:797 -803[Abstract]
  22. Goldman L, Weinberg M, Weisberg M, et al. A computer-derived protocol to aid in the diagnosis of emergency room patients with acute chest pain. N Engl J Med 1982;307 : 588-596[Abstract]
  23. Lee TH, Juarez G, Cook EF, et al. Ruling out acute MI: a prospective multicenter validation of a 12-hour strategy for patients at low risk. N Engl J Med 1991;324 : 1239-1246[Abstract]
  24. Sallach SM, Nowak R, Hudson MP, et al. A change in serum myoglobin to detect acute MI in patients with normal troponin I levels. Am J Cardiol 2004; 94:864 -867[CrossRef][Medline]
  25. Chaitman BR, Bourassa MG, Davis K, et al. Angiographic prevalence of high-risk coronary artery disease in patient subsets (CASS). Circulation 1981;64 : 360-367[Abstract/Free Full Text]
  26. Roe MT, Harrington RA, Prosper DM, et al. Clinical and therapeutic profile of patients presenting with acute coronary syndromes who do not have significant coronary artery disease. The Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) Trial Investigators. Circulation 2000;102 : 1101-1106[Abstract/Free Full Text]
  27. Wallentin L, Lagerqvist B, Husted S, Kontny F, Ståhle E, Swahn E. Outcome at 1 year after an invasive compared with a non-invasive strategy in unstable coronary-artery disease: the FRISC II invasive randomised trial. FRISC II Investigators. Fast Revascularisation During Instability in Coronary Artery Disease. Lancet 2000;356 : 9-16[CrossRef][Medline]
  28. Wallentin L. Non-ST-elevation acute coronary syndrome: fuel for the invasive strategy. Lancet 2002;360 : 738-739[CrossRef][Medline]
  29. Shabestari AA, Abdi S, Akhlaghpoor S, et al. Diagnostic performance of 64-channel multislice computed tomography in assessment of significant coronary artery disease in symptomatic subjects. Am J Cardiol 2007; 99:1656 -1661[CrossRef][Medline]
  30. Lau J, Ioannidis JP, Balk EM, et al. Diagnosing acute cardiac ischemia in the emergency department: a systematic review of the accuracy and clinical effect of current technologies. Ann Emerg Med2001; 37:453 -460[CrossRef][Medline]
  31. Janne d'Othée B, Siebert U, Cury R, Jadvar H, Dunn EJ, Hoffmann U. A systematic review on diagnostic accuracy of CT-based detection of significant coronary artery disease. Eur J Radiol2008; 65:449 -461[CrossRef][Medline]
  32. Kuntz KM, Fleischmann KE, Hunink MG, Douglas PS. Cost-effectiveness of diagnostic strategies for patients with chest pain. Ann Intern Med 1999; 130:709 -718[Abstract/Free Full Text]
  33. Arias E. United States life tables, 2003. Natl Vital Stat Rep 2006; 54:1 -40[Medline]
  34. Armstrong PW, Fu Y, Chang WC, et al. Acute coronary syndromes in the GUSTO-IIb trial: prognostic insights and impact of recurrent ischemia. The GUSTO-IIb Investigators. Circulation1998; 98:1860 -1868[Abstract/Free Full Text]
  35. Pope JH, Aufderheide TP, Ruthazer R, et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med 2000; 342:1163 -1170[Abstract/Free Full Text]
  36. Lalonde L, Clarke AE, Joseph L, Mackenzie T, Grover SA. Comparing the psychometric properties of preference-based and nonpreference-based health-related quality of life in coronary heart disease. Canadian Collaborative Cardiac Assessment Group. Qual Life Res1999; 8:399 -409[CrossRef][Medline]
  37. [No authors listed]. Coronary artery surgery study (CASS): a randomized trial of coronary artery bypass surgery—quality of life in patients randomly assigned to treatment groups. Circulation 1983;68 : 951-960[Abstract/Free Full Text]
  38. Centers for Medicare & Medicaid Services. Physician fee schedule relative value files. www.cms.hhs.gov/PhysicianFeeSched/PFSRVF/list.asp#TopOfPage.2005. Accessed April 27, 2007
  39. Hsiao WC, Braun P, Dunn D, Becker ER. Resource-based relative values: an overview. JAMA 1988;260 : 2347-2353[Abstract/Free Full Text]
  40. Lindsell CJ, Anantharaman V, Diercks D, et al. The Internet Tracking Registry of Acute Coronary Syndromes (i*trACS): a multicenter registry of patients with suspicion of acute coronary syndromes reported using the standardized reporting guidelines for emergency department chest pain studies. Ann Emerg Med 2006;48 : 666-677[CrossRef][Medline]
  41. Berman DS, Hachamovitch R, Shaw LJ, et al. Roles of nuclear cardiology, cardiac computed tomography, and cardiac magnetic resonance: assessment of patients with suspected coronary artery disease. J Nucl Med 2006; 47:74 -82[Abstract/Free Full Text]
  42. Drummond M, McGuire A, eds. Economic evaluation in health care: merging theory with practice. New York, NY: Oxford University Press, 2008:256 -276
  43. Drummond M, Pang F. Transferability of economic evaluation results. In: Drummond M, McGuire A, eds. Economic evaluation in health care: merging theory with practice. New York, NY: Oxford University Press, 2001: 256-276
  44. Garber AM, Solomon NA. Cost-effectiveness of alternative test strategies for the diagnosis of coronary artery disease. Ann Intern Med 1999; 130:719 -728[Abstract/Free Full Text]
  45. Peterson ED, Coombs LP, DeLong ER, Haan CK, Ferguson TB. Procedural volume as a marker of quality for CABG surgery. JAMA2004; 291:195 -201[Abstract/Free Full Text]
  46. Anderson HV, Shaw RE, Brindis RG, et al. A contemporary overview of percutaneous coronary interventions. The American College of Cardiology–National Cardiovascular Data Registry (ACC-NCDR). J Am Coll Cardiol 2002;39 : 1096-1103[Abstract/Free Full Text]
  47. Caro JJ, Trindade E, McGregor M. The risks of death and of severe nonfatal reactions with high- vs low-osmolality contrast media: a meta-analysis. AJR 1991;156 : 825-832[Abstract/Free Full Text]
  48. Cohen DJ, Bakhai A, Shi C, et al. Cost-effectiveness of sirolimus-eluting stents for treatment of complex coronary stenoses: results from the Sirolimus-Eluting Balloon Expandable Stent in the Treatment of Patients With De Novo Native Coronary Artery Lesions (SIRIUS) trial. Circulation 2004;110 : 508-514[Abstract/Free Full Text]
  49. Reynolds MR, Neil N, Ho KK, et al. Clinical and economic outcomes of multivessel coronary stenting compared with bypass surgery: a single-center US experience. Am Heart J 2003;145 : 334-342[CrossRef][Medline]
  50. Drugstore.com Website. www.drugstore.com.2007 . Accessed July 1, 2007

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
 RadiologyHome page
G. Bastarrika, Y. S. Lee, W. Huda, B. Ruzsics, P. Costello, and U. J. Schoepf
CT of Coronary Artery Disease
Radiology, November 1, 2009; 253(2): 317 - 338.
[Abstract] [Full Text] [PDF]

Home page
 Health Aff (Millwood)Home page
J. A. Ladapo, J. R. Horwitz, M. C. Weinstein, G. S. Gazelle, and D. M. Cutler
Adoption And Spread Of New Imaging Technology: A Case Study
Health Aff., November 1, 2009; 28(6): w1122 - w1132.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Roentgenol.Home page
G. Bastarrika, C. Thilo, G. F. Headden, P. L. Zwerner, P. Costello, and U. J. Schoepf
Cardiac CT in the Assessment of Acute Chest Pain in the Emergency Department
Am. J. Roentgenol., August 1, 2009; 193(2): 397 - 409.
[Abstract] [Full Text] [PDF]

Home page
 RadiologyHome page
E. J. Halpern
Triple-Rule-Out CT Angiography for Evaluation of Acute Chest Pain and Possible Acute Coronary Syndrome
Radiology, August 1, 2009; 252(2): 332 - 345.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Roentgenol.Home page
J. M. May, W. P. Shuman, J. N. Strote, K. R. Branch, L. M. Mitsumori, D. W. Lockhart, and J. H. Caldwell
Low-Risk Patients With Chest Pain in the Emergency Department: Negative 64-MDCT Coronary Angiography May Reduce Length of Stay and Hospital Charges
Am. J. Roentgenol., July 1, 2009; 193(1): 150 - 154.
[Abstract] [Full Text] [PDF]

Home page
 NEJMHome page
A. C. McCulloch, S. Paulin, S. K. Gerard, G. Karthikeyan, G. Vorobiof, W. M. Fogarty Jr., J. A.C. Lima, J. M. Miller, the CORE 64 Investigators, J. Walsh, et al.
Coronary Angiography by 64-Row CT
N. Engl. J. Med., May 7, 2009; 360(19): 2027 - 2031.
[Full Text] [PDF]

Home page
 Circ Cardiovasc ImagingHome page
U. Hoffmann and F. Bamberg
Is Computed Tomography Coronary Angiography the Most Accurate and Effective Noninvasive Imaging Tool to Evaluate Patients With Acute Chest Pain in the Emergency Department?: CT Coronary Angiography Is the Most Accurate and Effective Noninvasive Imaging Tool for Evaluating Patients Presenting With Chest Pain to the Emergency Department
Circ Cardiovasc Imaging, May 1, 2009; 2(3): 251 - 263.
[Full Text] [PDF]

Home page
 Circ Cardiovasc ImagingHome page
R. C. Hendel
Is Computed Tomography Coronary Angiography the Most Accurate and Effective Noninvasive Imaging Tool to Evaluate Patients With Acute Chest Pain in the Emergency Department?: CT Coronary Angiography Is the Most Accurate and Effective Noninvasive Imaging Tool for Evaluating Patients Presenting With Chest Pain to the Emergency Department: Antagonist Viewpoint
Circ Cardiovasc Imaging, May 1, 2009; 2(3): 264 - 275.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ladapo, J. A.
Right arrow Articles by Gazelle, G. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ladapo, J. A.
Right arrow Articles by Gazelle, G. S.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?
Hotlight (NEW!)
Right arrow
What's Hotlight?

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS