Comparison of High-Sensitivity C-Reactive Protein vs C-reactive Protein for Cardiovascular Risk Prediction in Chronic Cardiac Disease

Background: High-sensitivity C-reactive protein (hs-CRP) is a biomarker used for risk prediction for cardiovascular disease by assessing low concentration of inflammation. Measurements of regular CRP have become very sensitive with a lower detection limit of 0.3 mg/L. This study aimed to compare and explore the association between CRP and hs-CRP. Methods: Data from 607 consecutive patients referred for cardiovascular risk assessment with hs-CRP were reviewed retrospectively. In total, 570 patients were included in the analysis and classified into 3 (low-, medium-, and high-risk) groups (hs-CRP cutoff: <1, 1-3, >3 mg/L). Correlation between hs-CRP and CRP was assessed with the kappa statistic and visualized with a Bland-Altman plot. The association between hs-CRP and occurrence of the composite outcome (acute myocardial infarction, stroke, coronary intervention [percutaneous coronary intervention or bypass surgery], or death) was determined with Cox regression analysis and visualized with Kaplan-Meier curves. Results: A total number reclassification occurred in 8.6% of the cases for CRP risk groups, which demonstrates an agreement of 91.4% (kappa 0.87; P < 0.001). The correlation between CRP and hs-CRP was significant (P < 0.001), Spearman regression R-2 = 0.98. A Bland-Altman plot displayed an average difference of 0.19 mg/L (95%CI, 0.17 to 0.23) between the CRP and hs-CRP. Cardiovascular events were more likely to occur in patients who were older, with hs-CRP or CRP >3 mg/L and a history of coronary artery disease. Conclusions: The usual laboratory tests for CRP values in the lower range highly correlate with the hs-CRP tests and can therefore replace the costlier hs-CRP measurements.