Background: The prognoses of patients with false-negative test results by myocardial single photon emission computed tomography (SPECT) and by stress echocardiography are known to be different; the prognosis with false-negative SPECT is better in suspected and proven coronary artery disease (CAD).
Methods and results: Three strategies by which to diagnose CAD were compared for their cost-effectiveness when considering the prognostic value of false-negative results: (1) stress myocardial SPECT by dipyridamole or adenosine followed by coronary angiography (CAG), (2) exercise stress echocardiography followed by CAG, and (3) dobutamine stress echocardiography followed by CAG. Delta quality-adjusted life-year (QALY) was calculated for the three strategies separately when annual mortality and infarction rates were 0.5% and 0.5% for myocardial SPECT and 2% and 2% for stress echocardiography, respectively. Costs were estimated and costs per DeltaQALY were calculated according to the pretest likelihood of CAD (pCAD). The myocardial SPECT followed by CAG strategy was the most cost-effective in the patients with a pCAD of 0.3 or greater, and the dobutamine echocardiography followed by CAG strategy was the most cost-effective in patients with a pCAD of 0.2 or lower. This was the case when we assumed that the nondiagnostic test rate of dobutamine echocardiography was 9% (in contrast to 0% by myocardial SPECT and 18% by exercise echocardiography). Sensitivity analysis showed that the cost-effectiveness of dobutamine echocardiography followed by CAG was best only if the prognosis of false-negative results of dobutamine echocardiography was better. The cost-effectiveness of exercise echocardiography was dubious because of the high nondiagnostic rate with inadequate exercise.
Conclusions: When the lower event rates of (false) negative SPECT were considered, the relatively expensive myocardial SPECT strategy was more cost-effective than the cheaper stress echocardiography strategy in patients with a pCAD of 0.3 or greater. According to sensitivity analysis, the prognostic value of false-negative results and the nondiagnostic test rate were important determinants of stress myocardial study cost-effectiveness.