High-sensitivity C-reactive Protein Assay Research Articles

Performance characteristics of an automated high-sensitivity C-reactive protein assay on the Dimension RXL analyzer

Background: C-reactive protein (CRP) is a nonspecific marker of inflammation that can be used as a marker for atherosclerotic risk. This application requires increased precision at low CRP concentrations compared to traditional assays. Methods: The Dimension RXL is an automated chemistry analyzer for central laboratory use. The limit of detection, limit of quantification, linearity and imprecision of a high-sensitivity CRP assay developed for it were assessed. Method comparison studies were performed using samples both inside and outside the reference interval. The presence of a prozone effect was also evaluated. Results: The limit of detection was 0.7 mg/l. The method was linear from 2 to 60 mg/l and from 1 to 60 mg/l using systematic error limits of 10% and 20%, respectively. The total imprecision was <10% for CRP concentrations above 1.5 mg/l. No prozone effect was seen at a CRP concentration of 450 mg/l, the highest concentration tested. Using samples from 212 apparently healthy adults, the Dimension RXL method demonstrated good concordance with the BN II high-sensitivity CRP method for samples in the highest quartile. It also compared well using samples with elevated CRP concentrations. Conclusions: The Dimension RXL high-sensitivity CRP method may be adequate for atherosclerotic risk prediction in clinical practice if accurate and precise measurement is only required for the highest quartile. However, the total error of this method for CRP concentrations <3 mg/l appears too large for accurate assignment to lower risk groups.

Highly effective reduction of C-reactive protein in patients with coronary heart disease by extracorporeal low density lipoprotein apheresis

An association between C-reactive protein (CRP) and coronary heart disease (CHD) has been shown. CRP is present in atherosclerotic lesions, and there is increasing evidence that it may contribute to inflammation. Reduction of CRP concentrations otherwise considered normal may thus be of therapeutic value. Heparin-induced extracorporeal low density lipoprotein precipitation (HELP) is an established apheresis procedure to treat CHD patients with hypercholesterolemia. CRP concentrations were determined pre- and post-apheresis in 13 hypercholesterolemic CHD patients, during a total of 31 treatment procedures as well as in the interval between two treatments in six-patients using a high-sensitivity CRP assay. In addition, the effect of the HELP precipitation buffer on serum CRP concentrations was investigated in vitro. HELP treatment reduced CRP concentrations on average by 65%. The presence of CRP in the LDL precipitate of a patient was also confirmed by Western-blot analysis. In vitro experiments with serum samples revealed that CRP was partly co-precipitated with LDL. Greater fluctuation was observed in the post-apheresis concentrations of CRP compared with LDL. These results show that CRP can be very effectively lowered in CHD patients through the HELP system. This may further explain the stabilization and reduction of atherosclerotic plaques in hypercholesterolemic patients previously demonstrated with this treatment procedure.

Ultrarapid, Ultrasensitive One-Step Kinetic Immunoassay for C-Reactive Protein (CRP) in Whole Blood Samples: Measurement of the Entire CRP Concentration Range with a Single Sample Dilution

Recently, measurement of very low concentrations of C-reactive protein (CRP) has gained popularity as a potential new means for predicting the risk of future cardiac complications. In this study, we demonstrate the feasibility of a kinetic, one-step microparticle assay for quantitative determination of extremely low and high CRP concentrations in the limited timeframe typical for point-of-care testing. A noncompetitive, kinetic CRP immunoassay was developed that uses individual, porous microparticles as the solid phase. The microparticles were covalently coated with a monoclonal capture antibody, and the monoclonal detection antibody was labeled with europium. The one-step binding reaction was stopped by washing after 2 min of incubation, and the fluorescence signal of individual particles was measured. The analytical detection limit (mean of zero calibrator + 3 SD) was 0.00016 mg/L CRP. Clinical samples were diluted 400-fold before assay to cover the CRP concentration range of 0.064-1200 mg/L. The assay correlated well with the Dade Behring N High Sensitivity CRP assay (for 0-10 mg/L, r = 0.969, S(y/x) = 0.68, n = 54; for 0-350 mg/L, r = 0.969, S(y/x) = 11.7, n = 100). The within- and between-run CVs based on calculated concentrations were, respectively, 9-16% and 14% at 0.11 mg/L, 4.5-12% and 8.2% at 4.2 mg/L, and 3.5-6.3% and 4.4% at 105 mg/L, with a CV <15% at 0.2 mg/L and above. Use of the kinetic microparticle approach combined with time-resolved fluorometry allows ultrasensitive quantification of CRP in whole blood in 2 min with a linear assay range spanning more than four orders of magnitude.

High Sensitivity C-reactive Protein: An Emerging Role in Cardiovascular Risk Assessment

Coronary heart disease (CHD) is the major cause of death in the developed world and screening for conventional cardiovascular risk factors fails to identify more than 50% of the individuals who will present with acute coronary syndromes. Chronic inflammation appears to play a significant role in the initiation and development of atherosclerosis. Recent investigations have shown an association between inflammatory markers such as C-reactive protein (CRP) and CHD. These markers have proven useful as prognostic indicators in acute coronary syndromes and in predicting future coronary events in apparently healthy men and women. The availability of high sensitivity CRP (hs-CRP) assays has been crucial in exploring the role of this acute phase reactant in primary prevention settings. In this review, we discuss the evidence associating these inflammatory markers, especially CRP, with the pathogenesis of atherosclerosis and acute coronary syndromes, and we address the mechanism of risk as well as the clinical utility of this marker.

Inflammation and atherosclerosis: the value of the high-sensitivity C-reactive protein assay as a risk marker.

C-reactive protein (CRP) is a prototypic marker of inflammation. Numerous prospective studies in healthy volunteers have confirmed that high-sensitivity CRP (hsCRP) predicts cardiovascular events (CVEs), and hsCRP seems additive to an elevated total cholesterol level and a total/high-density lipoprotein cholesterol ratio in men and women in predicting risk. In smokers and people with metabolic syndrome, hsCRP levels are elevated; in elderly people, there seems to be a relationship between hsCRP and CVEs and mortality. Several properties of CRP make it proatherogenic; however; pending further studies, it should be considered as a risk marker. In people with acute coronary syndromes, hsCRP measurement may be valuable. Elevated levels in the highest quantile seem to predict greater mortality and poorer prognosis in patients with unstable angina and myocardial infarction (MI). While hsCRP is a strong independent predictor of risk of future MI, stroke, peripheral arterial disease, and vascular death, the validity of hsCRP as a risk marker needs to be assessed in all populations. Weight loss, statin drugs, aspirin, and high-dose alpha tocopherol therapy could affect hsCRP. It has its greatest validity as an adjunctive measure in the primary prevention of cardiovascular disease.

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

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 …

Medical-economical aspects of high sensitivity C-reactive protein assay for the prediction of coronary heart disease: an analysis in Germany and Italy

BACKGROUND Elevated plasma concentrations of C-reactive protein (CRP) are associated with increased cardiovascular risk. We studied the cost-effectiveness of CRP determination in primary and secondary prevention settings in two European countries: Germany and Italy. METHODS Using a decision analytic model we evaluated the costs and consequences of testing or not testing using a high sensitivity (hs)-CRP assay. In a primary prevention model we analyzed a hypothetical cohort of 300000 apparently healthy men divided into three age groups (35-44, 45-54 and 55-64 years). Individuals with CRP levels > 3 mg/l were administered either aspirin or statins according to lipid levels. The cohort was followed for 5 years. In the secondary prevention model hs-CRP testing was evaluated in a cohort of 10000 patients with total cholesterol levels < 4.52 mmol/l and a history of myocardial infarction or unstable angina. The two strategies tested were: 1) administer pravastatin only to those with high CRP values, and 2) treat all patients. The analysis was performed from the societal perspective. Event rates were obtained from epidemiological studies and clinical trials. RESULTS In the primary prevention model, strategies including testing showed, for men aged 45 years and older, cost-effectiveness ratios between each life year saved (LYS) and cost savings in Germany equal to 10217euro and between each LYS and savings in Italy equal to 16950euro In the age group 35-44 years, therapy with aspirin showed cost-effectiveness ratios of 5318euro and 11203euro per LYS in Germany and in Italy respectively. The widespread use of statins showed an unfavorable cost-effectiveness profile: 44630euro per LYS in Germany and 36270euro per LYS in Italy. In the secondary prevention model, hs-testing for CRP can reduce the cost-effectiveness of pravastatin from 16400 to 6830euro per quality adjusted life year gained. Sensitivity analysis performed on the variables test price and costs of cardiovascular events resulted in minimal changes of the cost-effectiveness ratios. CONCLUSIONS Both in the primary and the secondary prevention settings, hs-testing for CRP can better target individuals at higher risk, thus improving outcomes and resulting in a more cost-effective strategy.

Evaluation of four automated high-sensitivity C-reactive protein assays

Evaluation of four automated high-sensitivity C-reactive protein assays

High-Sensitivity C-Reactive Protein: A Novel and Promising Marker of Coronary Heart Disease

Coronary heart disease remains the leading cause of morbidity and mortality in the industrialized world. Clinical and laboratory studies have shown that inflammation plays a major role in the initiation, progression, and destabilization of atheromas. C-Reactive protein (CRP), an acute phase reactant that reflects low-grade systemic inflammation, has been studied in a variety of cardiovascular diseases. Findings from prospective clinical trials were examined to determine the prognostic utility of CRP in acute coronary syndromes, and observations from epidemiological studies were reviewed to determine the ability of CRP to predict future first coronary events. The analytical considerations of CRP measurement in these clinical applications were also examined. In patients with established coronary disease, CRP has been shown to predict adverse clinical events. In addition, prospective studies have consistently shown that CRP is a strong predictor of future coronary events in apparently healthy men and women. The relative risk associated with CRP is independent of other cardiovascular disease risk factors. High-sensitivity CRP (hs-CRP) assays are needed for risk assessment of cardiovascular disease. Such assays are currently available but may require further standardization because patients' results will be interpreted using population-based cutpoints. Preventive therapies to attenuate coronary risk in individuals with increased hs-CRP concentrations include aspirin and statin-type drugs. hs-CRP has prognostic utility in patients with acute coronary syndromes and is a strong independent predictor of future coronary events in apparently healthy subjects.

Clinical Efficacy of an Automated High-Sensitivity C-Reactive Protein Assay

Prospective studies have shown that C-reactive protein (CRP) can be used to predict risk of future cardiovascular events. High-sensitivity methods for CRP (hs-CRP) measurement are needed for this purpose. We compared the clinical efficacy of an automated and commercially available latex-enhanced assay (Latex) for hs-CRP (Dade Behring) to a validated in-house ELISA, previously shown to predict future peripheral arterial disease (PAD) in asymptomatic populations. Using a prospective, nested, case-control design, we measured baseline hs-CRP concentrations in 144 apparently healthy men who subsequently developed symptomatic PAD and 144 age- and smoking habit-matched controls who remained free of vascular disease over the follow-up period of 60 months. The two hs-CRP assays correlated highly (r = 0.95; P <0.001), and all but two participants were classified into concordant quartiles or varied by only one quartile. The median hs-CRP of the case group was significantly higher than that of controls when measured by either the ELISA (1.34 vs 0.99 mg/L; P = 0.034) or the Latex method (1.80 vs 1.20 mg/L; P = 0.042). Furthermore, for both ELISA and the Latex method, the calculated relative risks of developing PAD increased significantly with each increasing quartile of hs-CRP. The calculated interquartile increase in relative risk of PAD was 31% (95% confidence interval, 5.2-62.2%; P = 0.01) for ELISA and 34% (95% confidence interval, 8.2-66.1%; P = 0.007) for the Latex method. Our findings indicate that the Latex method is equally as efficacious as the validated ELISA in classifying patients into cutoff points established by prospective studies for risk stratification for coronary and cerebrovascular disease.