Combined Use of Computed Tomography Coronary Calcium Scores and C-Reactive Protein Levels in Predicting Cardiovascular Events in Nondiabetic Individuals

BACKGROUND: The South Bay Heart Watch is a prospective cohort study designed to appraise the value of coronary calcium and risk factors for predicting outcomes in asymptomatic adults. Two factors that may be related to subsequent cardiovascular events are coronary calcium (CAC, a manifestation of subclinical atherosclerosis) and high-sensitivity C-reactive protein (CRP, a measure of chronic inflammation). METHODS AND RESULTS: Between December 1990 and December 1992, 1461 participants without coronary heart disease underwent baseline risk factor screening, computed tomography for CAC, and measurement of CRP. Participants were followed up for 6.4+/-1.3 years. Cox regression analyses were conducted for the 967 nondiabetics with CRP levels < or =10 mg/L to estimate the risk-factor-adjusted relative risks of CAC and CRP for the occurrence of (1) nonfatal myocardial infarction (MI) or coronary death and (2) any cardiovascular event (MI, coronary death, coronary revascularization, or stroke). CAC was a predictor of both end points (P<0.005), and CRP was a predictor of any cardiovascular event (P=0.03). Risk group analysis defined by tertiles for CAC (<3.7, 3.7 to 142.1, >142.1) and the 75th percentile for CRP (>4.05 mg/L) indicated that there was increasing risk with increasing calcium and CRP. Relative risks for the medium-calcium/low-CRP risk group to high-calcium/high-CRP risk group ranged from 1.8 to 6.1 for MI/coronary death (P=0.003) and 2.8 to 7.5 for any cardiovascular event (P<0.001). CONCLUSIONS: Participants without diabetes and those at intermediate risk may benefit from risk stratification based on high-sensitivity CRP levels and CAC, because both factors contribute independently toward the incidence of cardiovascular events.