Economic Outcome of Cardiac CT-Based Evaluation and Standard of Care for Suspected Acute Coronary Syndrome in the Emergency Department

Rationale and Objectives

Cardiac computed tomography (CCT) in the emergency department may be cost saving for suspected acute coronary syndrome (ACS), but economic outcome data are limited. The objective of this study was to compare the cost of CCT-based evaluation versus standard of care (SOC) using the results of a clinical trial.

Materials and Methods

We developed a decision analytic cost-minimization model to compare CCT-based and SOC evaluation costs to obtain a correct diagnosis. Model inputs, including Medicare-adjusted patient costs, were primarily obtained from a cohort study of 102 patients at low to intermediate risk for ACS who underwent an emergency department SOC clinical evaluation and a 64-channel CCT. SOC costs included stress testing in 77% of patients. Data from published literature completed the model inputs and expanded data ranges for sensitivity analyses.

Results

Modeled mean patient costs for CCT-based evaluation were $750 (24%) lower than the SOC ($2384 and $3134, respectively). Sensitivity analyses indicated that CCT was less expensive over a wide range of estimates and was only more expensive with a CCT specificity below 67% or if more than 44% of very low risk patients had CCT. Probabilistic sensitivity analysis suggested that CCT-based evaluation had a 98.9% probability of being less expensive compared to SOC.

Conclusion

Using a decision analytic model, CCT-based evaluation resulted in overall lower cost than the SOC for possible ACS patients over a wide range of cost and outcome assumptions, including computed tomography–related complications and downstream costs.

In the United States, chest pain accounts for 5% of all emergency department (ED) visits and is a substantial economic and health resource burden . In 2008, the United States spent approximately $12 billion for the evaluation of acute chest pain . The current standard of care (SOC) for individuals presenting with possible acute coronary syndrome (ACS) often involves multiple tests over hours to days. Rest and stress single photon emission computed tomography is commonly used to test for myocardial ischemia with high sensitivity, but only after exclusion of myocardial damage. Multislice electrocardiogram (ECG)-gated computed tomography can rapidly differentiate multiple causes of symptomatic vascular disease including coronary artery disease (CAD) with high diagnostic sensitivity. As a result, use of ECG-gated thoracic computed tomography (CT) as part of a rapid evaluation in patients at low to intermediate risk of ACS may be less expensive than the SOC .

Previous economic model evaluations of cardiac CT (CCT) for evaluation of ACS suggested that CCT is less expensive than an SOC , but may be more costly with the inclusion of downstream costs associated with CT, such as iodinated contrast complications or incidental, noncardiac CT findings . However, no study to date has incorporated both actual ED patient costs and downstream costs associated with CCT.

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Methods

Study Design

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Patient Population and ED Evaluation

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Table 1

Patient Characteristics ( n = 102)

Characteristic Mean (95% CI) or n (%) Age (y) 54 (51–57) Male (%) 60 (59%) Caucasian (%) 78 (76%) Weight (kg) 86.5 (83–90) BMI 28.0 (27–29) TIMI ACS risk score 0.9 (0.7–1.1) Risk Factors (%) Hypertension 43 (42%) Dyslipidemia 39 (38%) Diabetes 9 (9%) Family history of premature CAD 39 (38%) Recent tobacco 18 (18%) Obesity 40 (39%) Sedentary lifestyle 45 (44%) Presenting Symptoms ∗ Chest pain 94 (92%) Syncope 4 (4%) Palpitations 2 (2%) Shortness of breath 1 (1%) Lightheadedness 1 (1%) Back pain 1 (1%)

ACS, acute coronary syndrome; BMI, body mass index; CAD, coronary artery disease; CI, confidence intervals; TIMI, Thrombolysis in Myocardial Infarction.

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Table 2

Model Parameters: Clinical Probabilities and Costs for the Decision Tree

Variable Name Baseline Value Range Distribution Data Origin or References ACS prevalence 0.07 0–0.2 Normal Patient data CCT sensitivity 1 0.85–1 Normal Patient data CCT specificity 0.88 0.65–0.9 Normal Patient data Stress test sensitivity (weighted mean) 0.85 0.77–0.94 Nuclear SPECT 0.86 0.81–0.96 Normal Echocardiogram 0.80 0.72–0.88 Stress test specificity (weighted mean) 0.76 0.68–0.83 Nuclear SPECT 0.74 0.67–0.91 Normal Echocardiogram 0.86 0.77–0.95 Hospital admission and cardiac catheterization 0.07 0–0.2 Normal Patient data Probabilities SOC arm cardiac stress testing 0.77 Patient data Nuclear SPECT 0.67 — Echocardiography 0.10 — — Patient data MI or unstable in ED (SOC arm only) Patient data Patients with ACS 0.05 0–0.3 Beta Patient data Patients without ACS 0.02 0–0.3 No SOC cardiac stress testing or catheterization 0.18 — — Patient data Incidental, noncardiac findings on SOC imaging requiring further evaluation 0 0.0008–0.01 Beta MI or death before diagnosis CCT arm 0 0–0.05 Beta Patient data SOC arm 0.01 0–0.05 Cardiac re-evaluation for recurrent symptoms 0.07 0–0.5 Beta Patient data CCT contrast complication 0 0.001–0.2 Beta Patient data CCT noncardiac finding CT noncardiac findings requiring repeat CT 0.04 0.04–0.09 Beta Patient data Positive repeat CT requiring PET 0.01 0–0.05 Costs ($USD) Base case cost for SOC arm $1841 $1739–$1944 Normal Patient data Base case cost for CCT arm $1521 $1464–$1578 Normal Patient data Hospital admission and cardiac catheterization $5524 $4420–$6629 Normal Patient data Cardiac catheterization $2773 $2218–$3327 Normal Patient data Iodinated contrast complication $897 $0–$76,317 Log normal Incidental, noncardiac CCT findings requiring repeat CT $448 $358–$538 Patient data Positive repeat CT requiring further evaluation $1255 $1004–$2644 Normal Patient data Cardiac re-evaluation for recurrent symptoms $1404 $256-$5524 Normal Patient data MI or death before ACS diagnosis $37,147 $7776–$117,490 Normal

ACS, acute coronary syndrome; CCT, cardiac computed tomography; CT, computed tomography; ED, emergency department; MI, myocardial infarction; PET, positron emission tomography; SOC, standard of care; SPECT, single photon emission computed tomography.

Costs were based on or adjusted to 2007 Medicare-based reimbursement amounts except for cardiac imaging costs which were based on 2010 Medicare reimbursements. Baseline costs were derived from patient data when available. The patient and literature data provided the range of values used for sensitivity and probabilistic Monte Carlo analyses. All costs were in US dollars ($).

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Decision Analytic Model

Decision tree

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Inputs and cost parameters

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Table 3

Common Billed Items Used to Determine Base Case Costs

Common ED Billed Items CPT Codes_n_ Mean per Patient ∗ Patients Billed for at Least One Item (%) Medicare Adjusted Cost † Complete blood count 85025, 85027 135 1.2 98 $9 Comprehensive metabolic panel 80053 60 0.7 58 $12 Basic metabolic panel 80048 75 0.9 47 $9 Troponin-I 84484 283 2.4 100 $14 D-dimer 85379 53 0.7 53 $14 Chest radiograph 71010, 71020 109 1.0 99 $66 Transthoracic echocardiogram 93307, 93320, 93325 5 0.1 4 $421 ED level of service 4 99284 9 — 9 $670 ED level of service 5 99285 93 — 93 $902 Cardiac testing ‡ Stress nuclear perfusion test 78464, 78465 67 — 67 $918 Stress echocardiogram 93350 10 — 10 $476 Invasive cardiac angiography 93545 7 — 7 $2773 No stress test — 18 — 18 $0 Cardiac CT 75574 102 1.0 100 $410

Comprehensive metabolic panel, basic metabolic panel plus liver function tests; ECG, electrocardiogram; ED, emergency department.

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Sensitivity and Probabilistic (Monte Carlo) Analysis

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Results

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Table 4

Cost for Correct Diagnosis for the Standard of Care and Cardiac CT-based Evaluation

Protocol Decision Analytic Model Mean Cost Mean Savings % Savings CCT Evaluation $2384 $750 24% SOC Evaluation $3134 — —

Protocol Probabilistic (Monte Carlo) Sensitivity Analysis Mean Cost (95% CI) Mean Savings (95% CI) % Savings (95% CI) CCT Evaluation $2385 ($1679–$3807) $750 ($681–$819) 24% (22%–27%) SOC Evaluation $3315 ($2490–$4462) — —

CCT, cardiac computed tomography; CT, computed tomography; SOC, standard of care.

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Sensitivity, Threshold, and Probabilistic Analyses

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Table 5

Modeled Costs for SOC and CCT Evaluations by ACS Prevalence and Type of Stress Test

Mean Cost Savings ($) CCT Savings (%) ACS prevalence 0% CT arm $2146 — — SOC $2964 $818 28 Stress nuclear $3043 $897 29 Stress echo $2413 $267 11 ACS prevalence 7% CT arm $2384 — — SOC arm $3134 $750 24 Stress nuclear $3208 $722 23 Stress echo $2617 $233 9 ACS prevalence 10% CT arm $2486 — — SOC arm $3207 $721 22 Stress nuclear $3278 $792 24 Stress echo $2617 $131 5 ACS prevalence 20% CT arm $2846 — — SOC arm $3449 $603 17 Stress nuclear $3514 $668 19 Stress echo $2996 $150 5

ACS, acute coronary syndrome; CCT, cardiac computed tomography; CT, computed tomography; SOC, standard of care.

Stress testing was performed in 77% of patients for all SOC cost calculations.

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Discussion

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Limitations

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Conclusions

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Supplementary data

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Appendix

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References

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Economic Outcome of Cardiac CT-Based Evaluation and Standard of Care for Suspected Acute Coronary Syndrome in the Emergency Department

Rationale and Objectives

Materials and Methods

Results

Conclusion

Methods

Study Design

Patient Population and ED Evaluation

Decision Analytic Model

Decision tree

Inputs and cost parameters

Sensitivity and Probabilistic (Monte Carlo) Analysis

Results

Sensitivity, Threshold, and Probabilistic Analyses

Discussion

Limitations

Conclusions

Supplementary data

References

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