LETTER TO THE EDITOR
Electron beam computed tomography in the diagnosis of obstructive coronary artery disease
Brahmajee K. Nallamothu, MD, MPHa,
Sanjay Saint, MD, MPHa,
Melvyn Rubenfire, MDa and
A. Mark Fendrick, MDa
a University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, Michigan 48109, USA
We congratulate the authors of the recent American College of Cardiology/American Heart Association Expert Consensus Document on Electron-Beam Computed Tomography (EBCT) for the Diagnosis and Prognosis of Coronary Artery Disease (CAD) on the publication of a fair and balanced review of the utility of EBCT in CAD (1). However, we would like to highlight four methodological limitations in their meta-analysis of the diagnostic accuracy of EBCT in obstructive CAD.
First, the authors state that after contacting investigators of the included studies, only two reports were excluded due to considerable patient overlap. Based on our communication with several of the investigators of these same reports, we believe there are additional studies that should have been excluded due to patient overlap. For instance, we know that all 491 subjects in the report by Detrano et al. (2) were later included in the multicenter analysis by Budoff et al. (3) (n = 710) (Detrano R, personal communication, July 1999), and that the studies by Bielak et al. (4) and Kaufmann et al. (5) had 100% patient overlap (Bielak LF, personal communication, May 1999). After eliminating other studies with potential overlap ( 50% overlap), we speculate that the Consensus Document overestimates the total number of subjects who have been studied with EBCT by almost one-third.
Second, it should be noted that the multicenter study by Budoff et al. (3), which is the largest single study in the meta-analysis, contains data from six institutions, each of which used independent protocols for performing EBCT examinations and for defining calcium on an EBCT film. Therefore, it would have been more appropriate to use center-specific data from each institution to calculate summary odds ratios and a summary receiver-operating-characteristic curve.
Third, we agree with the authors that the inclusion of reports that used diverse methods for assessing CAD, such as intravascular ultrasound (6) or historical information (history of prior myocardial infarction) (7), in their meta-analysis is likely to lead to substantial heterogeneity and inexact summary estimates. Finally, we know of at least three published studies missing from the Consensus Document that meet inclusion criteria for their meta-analysis (8–10).
Despite these limitations, however, we believe that the pooled estimates of sensitivity (90.5%) and specificity (49.2%) and the summary receiver-operating-characteristic curve provided in the Consensus Document are reasonably accurate; these findings correspond closely to the results of a recent systematic review of EBCT by our group that accounted for each of the limitations previously mentioned (11). Therefore, we agree with the authors’ conclusion that the overall accuracy of EBCT is likely to be similar, but not superior, to currently available noninvasive diagnostic tests in obstructive CAD.
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References
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1. O’Rourke RA, Brundage BH, Froelicher VF, et al. American College of Cardiology/American Heart Association Expert Consensus Document on electron-beam computed tomography for the diagnosis and prognosis of coronary artery disease. J Am Coll Cardiol. 2000;36:326–340[Free Full Text]
2. Detrano R, Hsiai T, Wang S, et al. Prognostic value of coronary calcification and angiographic stenoses in patients undergoing coronary angiography. J Am Coll Cardiol. 1996;27:285–290[Abstract]
3. Budoff MJ, Georgiou D, Brody A, et al. Ultrafast computed tomography as a diagnostic modality in the detection of CAD: a multicenter study. Circulation. 1996;93:898–904[Abstract/Free Full Text]
4. Bielak LF, Kaufmann RB, Moll PP, McCollough CH, Schwartz RS, Sheedy PF. Small lesions in the heart identified at electron beam CT: calcification or noise? Radiology. 1994;192:631–636[Abstract/Free Full Text]
5. Kaufmann RB, Sheedy PF, Maher JE, et al. Quantity of coronary artery calcium detected by electron beam computed tomography in asymptomatic subjects and angiographically-studied patients. Mayo Clin Proc. 1995;70:223–232[Abstract]
6. Schmermund A, Baumgart D, Adamzik M, et al. Comparison of electron-beam computed tomography and intracoronary ultrasound in detecting calcified and noncalcified plaques in patients with acute coronary syndromes and no or minimal to moderate angiographic CAD. Am J Cardiol. 1998;81:141–146[CrossRef][Medline]
7. Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Detrano R. Quantification of coronary artery calcium using ultrafast-computed tomography. J Am Coll Cardiol. 1990;15:827–832[Abstract]
8. Yao Z, Liu XJ, Shi R, et al. A comparison of 99mTc-MIBI myocardial SPET with electron beam computed tomography in the assessment of CAD. Eur J Nucl Med. 1997;24:1115–1120[Medline]
9. Yaghoubi S, Tang W, Wang S, et al. Offline assessment of atherosclerotic coronary calcium from electron beam tomograms. Am J Card Imaging. 1995;9:231–236[Medline]
10. Budoff MJ, Shavelle DM, Lamont DH, et al. Usefulness of electron beam computed tomography scanning for distinguishing ischemic from nonischemic cardiomyopathy. J Am Coll Cardiol. 1998;32:1173–1178[Abstract/Free Full Text]
11. Nallamothu BK, Saint S, Bielak LF, et al. Electron-beam computed tomography in the diagnosis of coronary artery disease: a meta-analysis. Arch Intern Med. In press.
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