High attributable risk of elevated C-reactive protein level to conventional coronary heart disease risk factors: the Third National Health and Nutrition Examination Survey

Abstract

Background: C-reactive protein (CRP), a marker of systemic inflammation, is predictive of coronary heart disease (CHD) events. However, the extent to which high CRP levels (>3 mg/L) may be attributable to high cholesterol levels and other CHD risk factors has not been well defined.

Methods: The prevalence of high CRP levels in the third National Health and Nutrition Examination Survey (n = 15 341) was studied using CHD risk-factor cut points designated as abnormal (total cholesterol values, >or=240 mg/dL [>or=6.22 mmol/L]; fasting blood glucose levels, >or=126 mg/dL [>or=6.99 mmol/L]; blood pressure, >or=140/90 mm Hg; body mass index [BMI], >or=30 kg/m(2); high-density lipoprotein cholesterol values, <40 mg/dL [<1.04 mmol/L] for men and <50 mg/dL [<1.30 mmol/L] for women; triglyceride levels, >or=200 mg/dL [>or=2.26 mmol/L]; current smoking status) or borderline (total cholesterol values, 200-239 mg/dL [5.18-6.19 mmol/L]; fasting blood glucose levels, 100-125 mg/dL [5.55-6.94 mmol/L]; blood pressure, 120-139/80-89 mm Hg; BMI, 25.0-29.9 kg/m(2), and triglyceride values 150-199 mg/dL [1.70-2.25 mmol/L], former smoking status), or normal.

Results: Weighted multiple logistic regression analysis demonstrated that high CRP level was significantly more common with obesity (odds ratio [OR], 3.78; 95% confidence interval [CI], 3.28-4.35]), overweight (OR, 1.88; 95% CI, 1.62-2.18), and diabetes (OR, 1.91; 95% CI, 1.54-2.38) and that high CRP level was rare in the absence of any borderline or abnormal CHD risk factor in men (4.4%) and women (10.3%). Overall, the risk of elevated CRP level attributable to the presence of any abnormal or borderline CHD risk factor was 78% in men and 67% women.

Conclusions: These data suggest that elevated CRP levels in the general population are in large measure attributable to traditional CHD risk factors. Moreover, CRP level elevation is rare in the absence of borderline or abnormal risk factors. As such, CRP measurements may have limited clinical utility as a screening tool beyond other known CHD risk factors.