Evaluation of Turbidimetric High-Sensitivity C-Reactive Protein Assays for Cardiovascular Risk Estimation

Abstract

Low-grade inflammation has been recognized as an important feature of atherosclerosis (1); therefore, markers of inflammation have been investigated for risk estimation of cardiovascular events (2)(3). However, in low-grade inflammations, C-reactive protein (CRP) concentrations are often lower than the measuring range of traditional CRP assays. For this purpose new assays, so-called high-sensitivity CRP (hs-CRP) assays, have been developed that cover a measuring range two orders of magnitude lower than those of the traditional assays (4). On the basis of hs-CRP results obtained in several cohort studies (5)(6)(7)(8), an algorithm using hs-CRP and lipid values was recently proposed for cardiovascular risk assessment (9). The aim of the present study was to evaluate four turbidimetric assays, suited for clinical chemistry analyzers, for analytical performance within the concentration range 0.7–3.9 mg/L, which has been proposed for cardiovascular risk assessment (9), in comparison with an established nephelometric assay. For precision and linearity studies we prepared serum pools from blood samples with previously measured hs-CRP (BN II nephelometer; Dade-Behring). The low and high pools were prepared by combining samples with hs-CRP <1 mg/L and 5–6 mg/L, respectively. The high pool was diluted with the low pool to the following final percentages of high pool: 100%, 75%, 50%, 30%, 20%, 10%, 5%, and 0%. The dilutions were aliquoted and stored at …