Nuclear cardiology in its over 40 years of use has grown to one of the most utilized and performed medical procedures in the United States, with cardiovascular imaging tests frequently being listed among the top 200 Medicare expenditures.^1–3 As nuclear cardiology has blossomed into an over $1 billion per year industry, increased attention and scrutiny have been given to this testing approach, particularly with cost-effectiveness playing a more central role. This has been seen in several different ways. Appropriate use criteria (AUC) have become mainstream tools in providing decision-making support as to whether or not a test or procedure is indicated based on evidence combined with expert consensus opinion.^4–6 This has contributed to a downtrend in the number of nuclear stress tests performed annually over the last decade (Fig. 20-1).⁷ In addition, in an era with continued technological advancements in each of the cardiac imaging modalities, clinicians often have multiple testing options that can be performed for a particular patient prompting a decision process that necessitates the evaluation of cost-effectiveness.^6,8

Since 2005, which reflected the peak years of nuclear cardiology reimbursement, there have been increased restrictions on referrals for diagnostic testing including preauthorization and test substitution, as well as reductions in reimbursement for location of testing performed (outpatient vs. hospital based). In addition, the Institute of Medicine in 2009 suggested that 30% or $750 billion per year was spent on unnecessary medical services,⁹ which puts all procedures under scrutiny. As the value of an imaging study becomes a pivotal issue, every diagnostic test must now pass individually defined quality and efficiency criteria. The value of the imaging study must balance the cost of the procedure with its impact on changing patient treatment and influencing outcomes. As the Medicare Access and CHIP Reauthorization Act (MACRA) of 2015 is implemented, the net value of the imaging procedure will directly impact on levels of reimbursement.

Thus, as the cost of diagnostic testing now plays a greater role in clinical decision making, clinicians have to be well educated in the science and economics of medicine as it impacts their daily practice. This chapter will discuss approaches to optimize the efficiency and quality of care based on patient selection for testing. This will be followed by a review of the definitions currently used for analysis and determination of cost-effectiveness. Finally, we will discuss sentinel studies that have examined value-based comparative approaches to diagnostic testing using nuclear stress tests as compared to other imaging modalities among patients presenting with stable ischemic heart disease or acute chest pain.

The value of a test can be directly correlated to the selection of an appropriate test for a particular patient. In 2005, the AUC were first released by the American College of Cardiology to help guide clinicians in the selection of nuclear stress tests for the most common indications.⁴ These were revised in 2009⁵ as the initial AUC document was incorporated into payer decisions for test reimbursement. The AUC for stable ischemic heart disease have been updated as part of a new set of multimodality AUC.⁶ This latest document also reflects changes in terminology to now include: appropriate, may be appropriate, and rarely appropriate.⁶ Refer to Chapter 13 for a more detailed discussion of AUC.

The use of clinical decision support for the selection of appropriate tests is mandatory for most commercial payers and is also a central portion of Medicare health care reform policies. The Protecting Access to Medicare Act of 2014 (PAMA) includes stipulations that require the use of clinical decision support tools as part of the reimbursement process for imaging including nuclear cardiology.⁸

The passing of the Affordable Care Act of 2010 in the United States brought increased attention to value-based purchasing,¹⁰ which examined health care value and included factors of quality and cost. Value-based purchasing can be mathematically written as:

From this equation, it is clear that value increases as either quality increases or costs decrease. However, how is quality defined? In general, quality has been expressed as efficiency relating the processes incorporated to attain a certain goal. In health care, it is often associated with outcomes, which include survival or quality of life.¹¹ For cost, the question remains for what period of time the cost is impacted (e.g., episode of care). In value-based imaging, for example, we can compare two test modalities such as an exercise treadmill stress test and a nuclear stress test. For the actual test performed, there is a monetary cost associated with the specific test, which is one portion of the diagnostic evaluation cost.¹² Based on the results of a certain test, additional diagnostic testing, procedures and/or treatments may be required, which result in a higher cost of the diagnostic test approach beyond the index procedure.¹³ However, over what timeframe do we allow these additional costs to be attributed to the index imaging procedure? There is as of yet no clear definition to incorporate associated downstream costs, but the length of time must be long enough to see the full benefit of the test and its subsequent results to fruition.¹⁴ Moreover, an episode of care can be quite short for an acute evaluation, but may also be protracted for lower risk, stable patients.

Cost-effectiveness in cardiac imaging may involve two different approaches and compares the costs and outcomes of these testing strategies. It is important to keep in mind that one of the comparators can be no testing at all.¹⁴ Quality-adjusted life-year (QALY) can be used to measure this outcome, which incorporates survival adjusted for quality of life.¹⁴ The incremental cost-effectiveness ratio (ICER) is the summed calculation and allows for comparison of two diagnostic approaches. This can be mathematically written (with 1 and 2 representing the two diagnostic tests) as:

It is important for the definition of cost-effectiveness to identify both absolute thresholds as well as the impact of selecting one modality over another while incorporating downstream-related expenses. The thresholds of QALY have varied in studies, but have often been designated as $50,000 in previous literature.^14,15 Recently, the World Health Organization has suggested an alternative calculation based on an individual country’s gross domestic product (GDP). Using the recommendation of three times the GDP would result in a new threshold in the United States of <$150,000 per life-year saved.¹⁴

The American College of Cardiology and the American Heart Association Task Force on Performance Measures and Task Force on Practice Guidelines now mandates that in addition to “Level of Evidence” for clinical guideline recommendations, that there also be a category of “Level of Value.”¹⁴ This proposal would include four categories: high value (H); intermediate value (I); low value (L); uncertain value (U). The dollar amount associated with these categories is linked with previously defined benchmarks of ICER (Table 20-1).

It has now been almost 20 years since one of the most sentinel papers regarding cost-effectiveness in cardiac imaging was published. The Economics of Noninvasive Diagnosis (END) Multicenter Study Group examined the cost impact of an approach using an initial referral for stress myocardial perfusion tomography versus direct referral for coronary angiography without initial noninvasive testing.¹⁶ In this study, 11,372 patients were prospectively evaluated for costs of care both in their initial diagnostic testing and in composite costs over a 3-year period. The costs of care using radionuclide myocardial perfusion imaging (range, $2,387–$3,010) were lower than for patients undergoing direct angiography (range, $2,878–$4,579) (p < 0.0001) despite similar rates of death or myocardial infarction (p > 0.20). Part of this increased cost was due to higher rates of revascularization among patients in the invasive arm. Reductions in cost were also seen due to only one-third of patients assigned to the initial imaging strategy undergoing subsequent coronary angiography. Although some interpreted these results as a license to use nuclear stress testing as a “gatekeeper,” it should instead be viewed as a precursor to trials such as COURAGE and BARI-2D, in that revascularization based solely on anatomic disease increases cost without a clinical benefit in terms of event-free survival (i.e., death or myocardial infarction-free survival).^17–19

Figure 20-2 shows a graph from the END Multicenter Study Group comparing both the diagnostic and follow-up costs for different clinical risk subsets of patients for stress-first versus invasive-first approaches. Upon review of this finding, several factors have to be kept in mind: (1) The dollar amounts in this figure reflect health care costs from 1995 which would clearly underestimate current costs¹⁶; (2) Both guideline-directed medical therapy and revascularization technologies have improved, which also underestimate the costs to both arms if reproduced at present day; (3) Referral patterns for patients undergoing ischemic heart disease evaluation have changed with recent studies showing lower abnormality rates for single-photon emission computed tomography (SPECT) testing.²⁰ These factors taken together would suggest a greater cost-effectiveness for a cardiac imaging first approach in stable ischemic heart disease.

In 1999, the Economics of Myocardial Perfusion Imaging in Europe (EMPIRE) study retrospectively examined 396 patients for the cost-effectiveness of several diagnostic strategies, as well as the quality of diagnosis in a patient population undergoing initial evaluation of suspected coronary artery disease.¹³ The diagnostic approaches evaluated in this trial were exercise stress testing, nuclear stress testing and coronary angiography with differentiation between institutions using nuclear stress testing routinely and for those who did not. The results from the EMPIRE study revealed that costs associated with both initial diagnostic approaches were reduced for institutions utilizing SPECT stress testing as well as a 32% lower 2-year diagnostic and management costs in these populations among patients without identified obstructive coronary artery disease. In patients where the algorithm was SPECT stress testing followed by coronary angiography versus angiography alone, 2-year costs were reduced 54% and 36% in patients without disease and those with disease, respectively, when using SPECT first (Fig. 20-3).¹³