C-reactive protein and electron beam tomography.

Beam Tomography To the Editor: The study by Park et al1 demonstrates that electron beam tomography (EBT)–derived coronary calcium scores (CCS) are incremental in predicting cardiac risk, consistent with previous data. However, the authors downplay the prognostic power of CCS and elevate the value of C-reactive protein (CRP). They state, “CRP was a marginally significant predictor of MI [myocardial infarction] or coronary death (P 0.09),” and, “CRP continued to contribute to the prediction of cardiovascular events (P 0.07) for MI/coronary death.” Are the authors suggesting that their predetermined level of significance of 0.05 is not correct? Lowering the standard for statistical significance will only increase the odds of a random event being deemed “significant.” In this study, the predictive power of CCS constituted most of the risk prediction, as the relative risk of hard cardiac events increased from 1 to 4.9 with increasing calcium tertiles (P 0.005). Increasing CRP among patients with low CCS raised the relative risk from 1.0 to 1.7 (P NS), and in the highest CCS tertile, from 4.9 to 6.1 (P NS). CRP, in this study, was not a significant predictor of hard cardiac events. The new National Cholesterol Education Program guidelines2 suggest that both of these new tests play a role in risk stratification. The most significant finding in the study by Park et al1 is that EBT-derived CCS is a potent predictor of cardiac events (P 0.0005), whereas CRP was only a modest predictor of total events (P 0.03). Additionally, the study by Park et al1 conspicuously avoids acknowledging EBT as the scanning technology. The exclusive use of computed tomography (CT), rather than EBT, appears to be an attempt to lump and equate EBT and multislice CT under the same umbrella. EBT calcium scoring is supported by hundreds of peer-reviewed articles, including all of the authors’ references. Goldin et al3 recently demonstrated that helical CT is not a substitute for EBT and cannot be used as a surrogate for determining CCS. Until such time as CCS by multislice CT achieves the same scientific validation as EBT, we urge continued distinction between the technologies. The authors conclude, “Participants without diabetes and those at intermediate risk may benefit from risk stratification based on high-sensitivity CRP levels and [coronary artery calcification].” This study’s cohort was at high risk, not intermediate risk. On the basis of Framingham risk estimates, the cohort (according to median values in Table 1 of the article1) had a 25% 10-year risk for nonsmokers and a 37% risk for smokers. The authors demonstrated the use of EBT-derived calcium scores strongly predicted future cardiac events in a high-risk cohort.