Coronary artery calcium score a cost-effective diagnostic approach for chest pain

When diagnosing patients who present with chest pain in Singapore, using a coronary artery calcium (CAC) score is deemed more efficient and cost-effective than a computerized tomography (CT) coronary angiogram.

In a cost modelling study that used observational data from the Cardiology Outpatient Clinic at the Singapore General Hospital (SGH), a diagnostic workup that categorizes patients into three (ie, for direct angiogram, further testing, or no testing) and involves using CAC score to refine risk stratification for low-risk patients (‘new practice’) could save SGD 764 in cost per patient as compared with the current practice of classifying patients by their risk and subsequently using a combination of treadmill tests, CAC scores, functional testing, and CT angiogram. [BMJ Open 2022;12:e050553]

If the ‘new practice’ were to replace the current, there is a 90-percent probability that the cost savings per patient are in the SGD 764–824 range and a 50-percent probability that they are in the SGD 616–912 range. This would yield a projected annual savings of SGD 11.5 million (range, 6.9–17.6) to SGH and of SGD 26.8 million (range, 16.2–41.1) to Singapore national health services.

The cost simulations included 10,622 new referrals to the National Heart Centre Singapore for investigation between January and December 2017 and represented accounting costs for 2018.

Cutting costs

Current testing approaches for the investigation of chest pain domestically are based on guidelines from the American College of Cardiology and Europe Society of Cardiology. The multiple methods available for evaluating patients have led to variation in physician practice, plausibly influenced by fear of medicolegal events and so defensive medicine arises, according to the study authors.

“[The current] analysis reveals some potential for cost savings from a decision to change the way patients referred to cardiology specialist clinics in Singapore are tested. Rather than use existing international guidelines that enable diverse approaches among clinicians, we modelled an evidence-based alternative that relies on CAC to inform risk assessment and subsequent decision making,” the authors said.

“Our primary conclusion is that patient safety could be maintained while saving resources and costs. This work will be useful for stakeholders interested in containing costs to Singapore health services,” given that approximately half of patients referred to cardiology specialist clinics per year have symptoms of chest pain that require diagnostic testing to rule out significant coronary artery disease (CAD), they added. [Ann Acad Med Singap 2008;37:103-108; BMJ Open 2017;7:e012652]

CAC and its merits

CAC score can be performed with a fraction of the time and cost of a CT coronary angiogram and has been shown to provide information to guide medication prescription that is comparable to functional cardiac testing.

“Prior studies at the National Heart Centre Singapore have demonstrated feasibility of the calcium score in detecting obstructive CAD. At a cutoff of 100, the sensitivity, specificity, and negative predictive value for detecting obstructive CAD were 73.2 percent, 84.8 percent, and 94.8 percent, respectively,” the authors noted.

Furthermore, when CAC was added to conventional risk factor variables and chest pain history, the prespecified cutoff risk score of ≤10 percent as gatekeeper for no further testing yielded a sensitivity of 89.3 percent and specificity of 74.7 percent in a model that includes cardiovascular risk factors, and 88.1 percent and 71.8 percent, respectively, in a model that excludes cardiovascular risk factors. Functional stress tests to diagnose CAD such as stress echocardiography and myocardial perfusion imaging tests had comparable sensitivities and specificities. [Clin Cardiol 2021;44:267-275]

“Finally, although the utility of CT calcium score in younger age groups of <50 years is less clear, there is growing evidence to show that the presence of coronary atherosclerosis have significantly higher risk for cardiovascular mortality… Selective use of screening for CAC might be considered in individuals with risk factors in early adulthood to inform discussions about primary prevention,” the authors said.

While the current data are valuable for early adopters and those motivated to make a practice change, the authors acknowledged that changing practices is likely to incur costs and that effective implementation of new models of care will require some large effort in terms of making time and, often, other resources to make the practice sustainable.

A future randomized clinical trial is needed to identify outcomes and endpoints that will resonate with clinicians, the authors said. “[It should be] pragmatic and established in the normal practice setting with a full range of study participants.”