Computed tomography for the measurement of coronary calcification in asymptomatic risk patients

BACKGROUND: In 2003 nearly 20% of deaths in Germany were caused by coronary heart disease (CHD). Risk models are used to estimate the ten-year-risk of a coronary event. Coronary calcification may be seen as an additional risk factor. The amount of calcium is correlated with atherosclerotic lesions, but there is no direct correlation with the probability of a plaque rupture. Coronary calcification may be measured either by electron beam computed tomography (EBCT) or multi-detector computed tomography (MDCT). OBJECTIVES: The aim of this HTA report is to investigate the diagnostic validity and cost effectiveness of computed tomography techniques in measuring coronary calcification of asymptomatic risk patients. Ethical aspects are discussed. METHODS: A systematic literature research was performed in 35 international databases which yielded 1080 articles. Overall 43 publications were included for assessment, according to predefined selection criteria. RESULTS: Measuring coronary calcification offers additional information compared with traditional risk factors. Yet at present it cannot be said - according to published literature - which population groups gain most. For determining adequate calcium score thresholds standardisation for age and sex is important. When comparing the reference standard EBCT with MDCT results are inconsistent and depend on the calcium-score value as well as on the scoring method. EBCT as a triage instrument in diagnosing CHD appears to be cost-effective. Yet it is rather not cost-effective as a refinement tool for risk stratification. DISCUSSION: Most of the literature was published in the United States and discusses the use of EBCT as well as (traditional) risk stratification by the Framingham Score. Regarding coronary calcification measured by MDCT (which is more widespread in Germany than EBCT) and a risk model applicable for European populations clear recommendations based on published literature cannot be made at present. CONCLUSION: In conclusion measuring coronary calcification is a promising tool for improving risk stratification with established risk models. Nevertheless many questions remain concerning the targeted use in medical practice, particularly regarding European populations. Therefore also no final conclusions can be drawn with respect to cost-effectiveness. The evaluation of diagnostic procedures measuring other parameters than coronary calcium with regard to CHD risk stratification, compared to EBCT or MDCT, is not part of this report.