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Re: Coronary calcium scoring the first step in case of suspected significant coronary atherosclerosis

With interest we read the article by Leschka and colleagues concerning the assessment of coronary atherosclerosis by dual-source computed tomography coronary angiography (CTCA) and calcium scoring (CS).[1] The authors propose an imaging pathway consisting of dual-source CTCA and selective CS in patients with suspicion of significant coronary atherosclerosis. We have two remarks.

Firstly, as the authors indicate in the Results and in Table 1 and 2, no significant stenoses were detected in patients without coronary calcium. However, in Figure 2, six patients without coronary stenosis are considered to have a negative calcium score. We assume this is an error and that this number should be zero. Then, the total number of patients with a calcium score of 0 or >= 400 add up to 46, consistent with the total number of patients mentioned under CS in Table 2.

The sensitivity of coronary calcium for presence of significant stenoses and the negative predictive value reported by the authors are 100%, in concordance with previous studies that used the gold standard, electron-beam tomography (EBT) to derive calcium scores.[2,3] In view of the reported negative predictive value, we propose that CS should be the initial test in case of suspected significant coronary atherosclerosis. Thus, further diagnostic imaging procedures with associated radiation dose and contrast effects can be withheld in almost one-fifth of the clinical population (14/74). Earlier generations of multi-detector computed tomography (MDCT) up to single source 64-MDCT were found to underestimate the amount of coronary calcium compared to EBT.[4] Thus, the prevalence of coronary calcium is underestimated with single-source MDCT, leading to unability to reliably exclude coronary calcium. With dual-source CT the temporal resolution of EBT is approximated. We recently found that dual- source CT-derived calcium scores are closer to calcium scores derived by EBT than those by MDCT.[5]

Dual-source CT studies in larger prospective populations should confirm these findings.

References

1. Leschka S, Scheffel H, Desbiolles L, et al. Combining dual-source computed tomography coronary angiography and calcium scoring: added value for the assessment of coronary artery disease. Heart 2008;94:1154-61. 2. Breen JF, Sheedy PF II, Schwartz RS, et al. Coronary artery calcification detected with ultrafast CT as an indication of coronary artery disease. Radiology 1992;185 : 435-439. 3. Laudon DA, Vukov LF, Breen JF, Rumberger JA, Wollan PC, Sheedy PF II. Use of electron-beam computed tomography in the evaluation of chest pain patients in the emergency department. Ann Emerg Med1999; 33:15 -21 4. Greuter MJ, Dijkstra H, Groen JM, et al. 64 slice MDCT generally underestimates coronary calcium scores as compared to EBT: a phantom study. Med Phys 2007;34:3510-9. 5. Groen JM, Greuter MJ, Vliegenthart R, et al. Calcium scoring using 64- slice MDCT, dual source CT and EBT: a comparative phantom study. Int J Cardiovasc Imaging 2008;24:547-56.