COST-EFFECTIVENESS OF DIAGNOSTIC TESTS FOR ASSESSING STABLE CHEST PAIN: SHOULD CARDIAC MAGNETIC RESONANCE AND CORONARY COMPUTED TOMOGRAPHY BE REIMBURSED BY A MIDDLE-INCOME COUNTRY'S PUBLIC HEALTHCARE SYSTEM?

    Purpose:   Proper evaluation and diagnosis of coronary artery disease (CAD) is an essential part of public health strategies. In Brazil, the Unified National Health System (SUS) currently reimburses exercise electrocardiogram (Ex-ECG), stress echocardiogram (ECHO), and single-photon emission computed tomography (SPECT), but not coronary computed tomography coronary angiogram (CT) or stress cardiac magnetic resonance (MRI). We sought to compare the cost effectiveness of different testing strategies, measured as cost per correct diagnosis.

   Methods: We built a decision-analytic model, comparing eleven strategies combining sequential tests (figure 1) for evaluating patients with possible stable angina, from the public health system's perspective. We used available data from published meta-analyses of test performance and 2013 SUS reimbursement rates as source of costs for diagnostic tests. The costs of CT and MRI were estimated based on costs in the private sector.  All results are expressed in International Dollars (I$). The main parameter test's performance and costs are: Ex-ECG (sensitivity 65%, specificity 67% and cost I$ 16.1), ECHO (sensitivity 85%, specificity 77% and cost I$ 88.7), SPECT (sensitivity 87%, specificity 64% and cost I$ 425.6), CT (sensitivity 88%, specificity 87% and cost I$ 102.7), MRI (sensitivity 89%, specificity 80% and cost I$ 203.8) and CA (sensitivity 100%, specificity 100% and cost I$ 330.5).

   Results: Figure 1 illustrates the cost-effectiveness results for each pretest probability. Strategies using Ex-ECG as initial test were the least costly alternatives, but showed the disadvantage of generating a larger number of false-positive initial tests and false-negative final diagnosis. Strategies 6 and 9, based on CT and ECHO as initial test, result in almost superposable cost-effectiveness results. Strategy 8, based on C-MRI, was highly effective for diagnosing stable CAD, but its relatively high cost resulted in unfavorable ICERs in moderate- and high-risk scenarios. Noninvasive strategies based on SPECT (3 and 5) generated consistently unfavorable results, due to the high cost of SPECT when compared to other noninvasive tests, and have been dominated in all scenarios.

   Conclusions: Incorporation of coronary computed tomography into SUS would add a cost-effective option for CAD diagnosis. Stress cardiac magnetic resonance yielded acceptable ICER only at low pretest probability. Stress echocardiography is an alternative option among currently available tests.