Shifting the Diagnostic Paradigm: A Novel Diagnostic Approach for Evaluating Suspected Coronary Artery Disease

MD Magazine Cardiology, May 2016, Volume 6, Issue 3

It's time to redirect the initial evaluation of low- to intermediate-risk patients presenting with symptoms suggestive of CAD back to the primary care and internal medicine setting.

The Call for a New Paradigm in Evaluating Suspected Coronary Artery Disease

The current diagnostic pathway for evaluating chest pain patients with suspected coronary artery disease (CAD) is fraught with numerous challenges, including ambiguity in clinical decision-making, an over-reliance on various testing modalities and, for many patients, needless expense. It is estimated that over $6.7 billion is spent annually in the US on noninvasive and invasive approaches for the workup of these patients.1 In many instances, the concern of avoiding a misdiagnosis that would lead to a cardiac event has created a management culture of “defensive medicine” and a reflex referral to cardiologists which, in turn, frequently results in abundant diagnostic testing of these patients and, in some cases, unnecessary cardiac procedures. Also, these noninvasive diagnostic tests may trigger the performance of therapeutic procedures such as angioplasty and stenting that, in a low-risk patient, may tilt the ratio of benefit and risk toward the latter. In the aggregate, the unfettered use of such diagnostic tests and the downstream procedures can be risky and costly to both patients and the healthcare system.

We need to redirect the initial evaluation of low- to intermediate-risk patients presenting with symptoms suggestive of CAD back to the primary care and internal medicine setting to enable these physicians to play a more prominent role in the initial evaluation and decision-making process.

The Value to the System and Patients Alike

The diagnosis and management of suspected CAD is extremely resource- and labor-intensive and creates a burden on emergency departments and challenges for outpatient practices. In the US alone, the evaluation of suspected CAD is associated with millions of stress tests and angiograms yearly. Importantly, of the patients presenting with symptoms, approximately 90% of those evaluated by primary care physicians (PCPs) are ultimately diagnosed with non-cardiac issues.2

The benefit of shifting physician decision-making, from routine cardiology specialty referral to the primary care physician and practicing internist, is that we can better risk-stratify patients with a lower risk profile and avoid unnecessary referral and procedures that have not been shown to be of any clinical benefit. This would result in better care and help alleviate the burden on the financial health of the managed care system while providing patients with a more selective and tailored approach to management and less expensive treatment.

Why We Need a New Management Paradigm for Assessing CAD

To evaluate chest pain in patients with suspected CAD, physicians have a vast array of noninvasive diagnostic tests from which to choose, including myocardial perfusion imaging, stress echocardiography, or coronary computed tomographic angiography, among others. Unfortunately, in many instances, noninvasive testing is inconclusive or non-definitive in establishing the presence or absence of obstructive disease. A common clinical scenario is that an initial noninvasive test culminates in an ambiguous or non-definitive result which, in turn, begets more diagnostic testing, or triggers a subspecialist referral. In short, noninvasive testing can become an open door to the cardiac catheterization laboratory and an invasive approach that is more appropriately reserved for the acutely ill or the more high-risk coronary patient. There is important evidence from recent clinical trials to support this. The NIH-funded PROMISE trial showed that 54% of patients who were referred to a cardiologist for coronary angiography didn't need it.3

How Can We Do Better?

One pathway to pivot the diagnostic evaluation of such low-risk patients back into the PCP setting and ensure the evaluation provides reliable information to the prescribing physician is to utilize the Corus CAD test, a simple blood test to assess one’s current risk of coronary disease obstruction, in the initial evaluation of suspected CAD. By doing so, we would more efficiently exclude low-risk patients from the sometimes risky and costly advanced cardiovascular diagnostic and therapeutic procedures that do not provide them clinical benefit.

The Corus CAD test can be conducted in either the doctor’s office or routine clinical laboratory. Results are available within a few days and are easy to interpret. This novel diagnostic test is reliable, safe, and cost-effective and is remarkably effective (96%) at excluding chest pain patients with obstructive CAD to help guide initial diagnostic decisions in low- to intermediate-risk patients.4 While tests involving gene expression are relatively new in cardiology, this type of testing has been used extensively elsewhere.

Unfortunately, many physicians believe that chest discomfort is an inevitable reflection of high cardiac risk and liability for potential misdiagnosis. But the reality is that we pay far too much attention to the high-risk end of the CAD risk spectrum, which probably comprises no more than 15% to 20% of all patients with suspected angina.5 Thus, in an era of steadily rising healthcare expenditures, burgeoning procedural utilization, and increasingly fragmented patient care, there is clearly an opportunity for practicing physicians to embrace a new diagnostic algorithm that seeks to employ a novel personalized medicine tool, like the Corus CAD test, to better diagnose and risk-stratify patients with suspected angina more efficiently.

References:

1. Hochheiser LI, Juusola JL, Monane M, et al. Economic utility of a blood-based genomic test for the assessment of patients with symptoms suggestive of obstructive coronary artery disease. Popul Health Manag. 2014;17(5):287-96.

2. Cayley WE. Diagnosing the Cause of Chest Pain. Am Fam Physician. 2005;72(10):2012-2021.

3. Douglas P, Hoffmann U, Patel M, et al. Outcomes of Anatomical versus Functional Testing for Coronary Artery Disease. N Engl J Med. 2015;372(14):1291-300.

4. The COMPASS study demonstrated that the Corus CAD algorithm has an NPV of 96% at the pre‐specified threshold of 15 in a population of men and women referred to MPI.

5. Eagle KA, Lim MJ, Dabbous OH, et al. A validated prediction model for all forms of acute coronary syndrome: estimating the risk of 6-month post-discharge death in an international registry. JAMA. 2004;291:2727-2733.

About the Author

William E. Boden, MD, FACC, FAHA, is chief of medicine at the Samuel S. Stratton VA Medical Center. He is also vice chairman of the Department of Medicine and professor of medicine at Albany Medical Center, Albany Medical College. Dr. Boden is a member of the scientific advisory board of CardioDx, maker of the Corus CAD test.