Prognostic Value of Cardiac Risk Factors and Coronary Artery Calcium Screening for All-Cause Mortality1

doi:10.1148/radiol.2283021006

Prognostic Value of Cardiac Risk Factors and Coronary Artery Calcium Screening for All-Cause Mortality1

¹From the American Cardiovascular Research Institute, Atlanta, Ga (L.J.S.); Division of Cardiology, Tulane University School of Medicine, 1430 Tulane Ave, SL48, New Orleans, LA 70112 (P.R.); Cedars-Sinai Medical Center, Los Angeles, Calif (E.S., D.S.B.); and EBT Research Foundation, Nashville, Tenn (T.Q.C.). Received August 14, 2002; revision requested October 15; final revision received March 11, 2003; accepted March 20. Address correspondence to P.R. (e-mail: praggi@tulane.edu).

Abstract

PURPOSE: To develop risk-adjusted multivariable models that included risk factors and coronary calcium scores determined with electron-beam computed tomography (CT) in asymptomatic patients for the prediction of all-cause mortality.

MATERIALS AND METHODS: We followed up a cohort of 10,377 asymptomatic individuals undergoing cardiac risk factor evaluation and coronary calcium screening with electron-beam CT. Multivariable Cox proportional hazards models were developed to predict all-cause mortality. Risk-adjusted models incorporated traditional risk factors for coronary disease and coronary calcium scores.

RESULTS: Cardiac risk factors such as family history of coronary disease (69%), hypercholesterolemia (62%), hypertension (44%), smoking (40%), and diabetes (9%) were prevalent. The frequency of coronary calcium scores was 57%, 20%, 14%, 6%, and 3% for scores of 10 or less, 11–100, 101–400, 401–1,000, and greater than 1,000, respectively. During a mean follow-up of 5.0 years ± 0.0086 (standard error of the mean), the death rate was 2.4%. In a risk-adjusted model (model χ² = 388.2, P < .001), coronary calcium was an independent predictor of mortality (P < .001). Risk-adjusted relative risk values for coronary calcium were 1.64, 1.74, 2.54, and 4.03 for scores of 11–100, 101–400, 401–1,000, and greater than 1,000, respectively (P < .001 for all values), as compared with that for a score of 10 or less. Five-year risk-adjusted survival was 99.0% for a calcium score of 10 or less and 95.0% for a score of greater than 1,000 (P < .001). With a receiver operating characteristic curve, the concordance index increased from 0.72 for cardiac risk factors alone to 0.78 (P < .001) when the calcium score was added to a multivariable model for prediction of death.

CONCLUSION: This large observational data series shows that coronary calcium provides independent incremental information in addition to traditional risk factors in the prediction of all-cause mortality.

Footnotes

Abbreviations: A_z = area under the ROC curve, ROC = receiver operating characteristic
Author contributions: Guarantors of integrity of entire study, L.J.S., P.R.; study concepts, L.J.S., P.R., D.S.B., T.Q.C.; study design, L.J.S.; literature research, L.J.S., D.S.B., P.R., T.Q.C.; clinical studies, T.Q.C., P.R.; data acquisition, L.J.S., P.R., T.Q.C.; data analysis/interpretation, D.S.B., P.R., L.J.S., E.S.; statistical analysis, L.J.S.. E.S.; manuscript preparation and definition of intellectual content, all authors; manuscript editing, revision/review, and final version approval, L.J.S., P.R.