Review: Exercise ECHO is a more specific and discriminatory test than exercise SPECT for coronary artery disease
ACP J Club. 1999 Mar-April;130:45. doi:10.7326/ACPJC-1999-130-2-045
Fleischmann KE, Hunink MG, Kuntz KM, Douglas PS. Exercise echocardiography or exercise SPECT imaging? A meta-analysis of diagnostic test performance. JAMA. 1998 Sep 9;280:913-20.
What is the diagnostic accuracy of exercise echocardiography (ECHO) and exercise single-photon emission computed tomography (SPECT) imaging in detecting coronary artery disease (CAD)?
Studies in humans were identified by searching MEDLINE (January 1990 to October 1997) using the terms coronary disease, exercise test, echocardiography, thallium, thallium radioisotopes, and sestamibi. Additional studies were obtained from bibliographies of original articles and reviews and by contacting experts.
Studies were selected if they investigated the use of ECHO or SPECT with thallium or sestamibi for the assessment of CAD, if angiography was used as the diagnostic standard, and if raw data were provided. Studies that exclusively evaluated patients with recent myocardial infarction, unstable angina, angioplasty, or coronary artery bypass grafting were excluded.
A radiologist and cardiologist independently extracted data on year of publication, patient characteristics (age, sex, indication, cardiac history, and setting), technical factors (definition of CAD, type of exercise and radioisotope used, and possible verification bias), and test performance.
Of 902 articles screened, 44 were evaluated (24 studies of ECHO with 2637 patients, and 27 studies of SPECT with 3237 patients). In a summary receiver-operating characteristic model that compared ECHO with SPECT, ECHO was associated with better discriminatory power. Both tests performed better than exercise electrocardiography alone (Table).
ECHO and SPECT are equally sensitive in the detection of CAD, but ECHO is more specific and has a higher discriminatory capacity.
Sources of funding: National Heart, Lung and Blood Institute; American Society of Echocardiography; Netherlands Organization for Scientific Research.
For correspondence: Dr. K.E. Fleischmann, Cardiovascular Division, University of California, San Francisco, Medical Center, 505 Parnassus Avenue, San Francisco, CA 94143-0214, USA. FAX 415-476-5875.
Table. Diagnostic test performances for exercise echocardiography (ECHO), exercise single-photon emission computed tomography (SPECT), and exercise electrocardiography (ECG) for coronary artery disease*
|Test||Patients||Sensitivity (95% CI)||Specificity (CI)||+LR||-LR|
|ECHO||All||85% (83 to 87)||77% (74 to 80)||3.7||0.19|
|No previous MI||87% (84 to 89)||84% (81 to 88)||5.4||0.15|
|SPECT||All||87% (86 to 88)||64% (60 to 68)||2.4||0.20|
|No previous MI||86% (83 to 88)||62% (55 to 70)||2.3||0.23|
|ECG||All||52% (50 to 55)||71% (68 to 74)||1.8||0.68|
*MI = myocardial infarction. Other abbreviations defined in Glossary. +LR and -LR calculated from data in article.
When 2 tests are available to help diagnose a condition, availability, accuracy, local expertise, and community standards are all important factors when deciding which test to use. For evaluation of patients with known or suspected CAD, the choice often must be made between exercise SPECT and exercise ECHO. Fleischmann and colleagues address the issue of accuracy by performing a meta-analysis of the current literature. They conclude that exercise ECHO is more accurate in diagnosing CAD than exercise SPECT based on a lower false-positive rate in ECHO (both had similar sensitivities).
In the studies cited, the accuracy of the exercise SPECT or ECHO was based on the test's ability to predict angiographic findings. As the authors commented, the prognostic capabilities of the tests were not addressed. Stress SPECT is a strong predictor of patient outcome. Current data are mixed and relatively limited on the prognostic capabilities of exercise ECHO (1, 2).
The prevalence of CAD (70%), the criteria for positivity of the exercise ECHO or SPECT, and the importance of the angiographic findings in the studies reviewed by Fleischmann and colleagues are not representative of many practices. The accuracies cited in the literature therefore can only serve as guidelines. Both tests have the potential to be useful, but because they are difficult to perform and accurately interpret, the decision of which test to use may rest on available expertise and the issues being addressed for each patient.
Martin Jacobs, MD
Kettering Medical CenterKettering, Ohio, USA
1. Brown KA. Do stress echocardiography and myocardial perfusion imaging have the same ability to identify the low-risk patient with known or suspected coronary artery disease? Am J Cardiol. 1998;81:1050-3.