C-reactive protein level and traditional vascular risk factors in the prediction of carotid stenosis.

Hypothesis: There is no relationship between C-reactive protein (CRP) level and the presence and degree of carotid stenosis (null hypothesis).

Design: Institutional review board-approved cohort study.

Setting: Tertiary care regional medical center.

Patients: Patients (N = 146) referred to a vascular surgery clinic for possible carotid stenosis.

Interventions: Baseline serum high-sensitivity CRP level, low-density lipoprotein cholesterol (LDL-C) level, and other traditionally used vascular risk factors were assessed in all patients. All underwent vascular surgery clinical examination, including bilateral duplex ultrasonography of their carotid bifurcations.

Main Outcome Measures: The potential relationship between serum CRP level and the presence and degree of carotid stenosis, as well as the strength of this association with traditionally established demographic, historical, and laboratory risk factors such as age, hypertension, and LDL-C level.

Results: In unadjusted analysis, CRP level, coronary artery disease (CAD), and lower extremity peripheral vascular disease (PVD) positively correlated with carotid stenosis (Pearson product moment correlation r < 0.02 for all). Low-density lipoprotein cholesterol level and other risk factors, including age, sex, race/ethnicity, smoking history, hypertension, diabetes mellitus, and neurologic history, did not. The mean +/- SD CRP level was higher among 72 patients with carotid stenosis compared with that among 74 patients without carotid stenosis (3.7 +/- 6.1 vs 1.9 +/- 2.1 mg/L [to convert to nanomoles per liter, multiply by 9.524], P =.02), as were the baseline prevalences of CAD (49% vs 29%), PVD (27% vs 11%), and (84% vs 61%) (P < .03 for all). The mean +/- SD LDL-C levels were similar between the groups (92.3 +/- 28.6 vs 95.8 +/- 29.0 mg/dL [to convert to millimoles per liter, multiply by 0.0259], P = .8), and differences in the prevalences of other risk factors were not statistically significant. In multivariate regression analysis adjusting for age, sex, race/ethnicity, smoking history, hypertension, diabetes mellitus, recent neurologic symptoms (<120 days), CAD, PVD, myocardial infarction, stroke or transient ischemic attack, hypercholesterolemia, aspirin or nonsteroidal anti-inflammatory drug use, and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) use, CRP level was independently associated with carotid stenosis (odds ratio [OR], 1.2; 95% confidence interval [CI], 1.1-1.5; P =.04), and LDL-C level was not (OR, 1.0; 95% CI, 0.98-1.01; P =.8). Several risk factors had larger ORs for carotid stenosis than CRP level; however, none were statistically significant. C-reactive protein level and CAD were independently associated with the actual degree of carotid stenosis in multivariate analysis. No corresponding associations for LDL-C level or other risk factors were observed.

Conclusion: C-reactive protein level is a moderate but statistically significant marker of carotid stenosis and may be a useful adjunct to accurate global vascular risk assessment.