High sensitivity immunoassays for C-reactive protein: promises and pitfalls

Electrochemical Detection of C-Reactive Protein in Human Serum Based on Self-Assembled Monolayer-Modified Interdigitated Wave-Shaped Electrode

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01-10,000 ng mL-1. The electrode showed detection limits of 0.025 ng mL-1 and 0.23 ng mL-1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Combined oral contraception and obesity are strong predictors of low-grade inflammation in healthy individuals: results from the Danish Blood Donor Study (DBDS)

BACKGROUND

C-reactive protein (CRP) is a well-established marker of inflammation. The level of CRP is affected by several lifestyle factors. A slightly increased CRP level, also known as low-grade inflammation (LGI), is associated with increased risk of several diseases, especially cardiovascular disease. The aim of this study was to identify predictors of increased CRP levels in healthy individuals. We therefore assessed CRP in a large cohort of blood donors.

METHODS

We measured plasma CRP levels in 15,684 participants from the Danish Blood Donor Study. CRP was measured by a commercial assay. Furthermore, all participants completed a standard questionnaire on smoking status, alcohol consumption, physical activity, diet, and various body measurements. Female participants also reported the use of contraception, childbirth, and menopausal status. The relationship between LGI (defined here as a plasma CRP level between 3 mg/L and 10 mg/L) and predictors was explored by multivariable logistic regression analysis. Results were presented as odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

We found LGI in a total of 1,561 (10.0%) participants. LGI was more frequent in women using combined oral contraception (OC) (29.9%) than in men (6.1%) and women not using OC (7.9%). Among premenopausal women, OC was the strongest predictor of LGI (odds ratio = 8.98, p<0.001). Additionally, body mass index (BMI) and waist circumference were positively associated with LGI.

CONCLUSION

High BMI and abdominal obesity strongly predicted LGI among healthy individuals. However, the most striking finding was the high prevalence of LGI among premenopausal women who used combined oral contraception. Although the significance of CRP as a marker of inflammation is well known, the role of CRP in pathogenesis is still uncertain. The impact of oral contraception on CRP levels should nevertheless be considered when CRP is used in risk assessment.

Neighborhoods and systemic inflammation: high CRP among legal and unauthorized Brazilian migrants

We estimate cross-sectional associations of neighborhood-level disorder, socioeconomic characteristics and social capital with individual-level systemic inflammation, measured as high C-reactive protein (CRP), using Boston Metropolitan Immigrant Health & Legal Status Survey (BM-IHLSS) data-a sample of relatively young, healthy foreign-born Brazilian adults. Logistic regression analyses suggest high CRP is positively associated with neighborhood disorder and negatively related to neighborhood social capital. Although we find no significant associations between other neighborhood socioeconomic variables and high CRP; males, those who were born in an urban area and those who had been graduated from high school were less likely to have had high CRP. Unauthorized Brazilian adults, those who smoked cigarettes daily and those who had a higher body mass index were more likely to have had high CRP. Our findings suggest that investigating sociogeographic stressors and social support may be important for understanding physiological dysregulation even among relatively healthy U.S. sub-populations.

A high sensitivity assay is more accurate than a classical assay for the measurement of plasma CRP levels in endometriosis

BACKGROUND

Endometriosis is associated with chronic subclinical inflammation. C-reactive protein (CRP), a marker of inflammation, could serve as a biomarker of endometriosis. We tested the hypothesis that a high sensitivity CRP assay (hsCRP) is more accurate than a classical CRP assay in the detection of subclinical inflammation in plasma of women with endometriosis.

METHODS

CRP levels were measured by hsCRP and classical CRP assays in plasma of 204 women with endometriosis and 91 women without endometriosis. Both assays were compared with respect to their value for the diagnosis of endometriosis.

RESULTS

The number of plasma samples with detectable CRP was significantly higher (100%) using the hsCRP assay when compared to the classical CRP assay (42.7%) (p < 0.0001). Significantly increased CRP plasma levels were found in women with endometriosis when compared with controls when the hsCRP assay was used in samples obtained during the luteal phase (p = 0.008). The highest discriminative ability for the diagnosis of endometriosis was also obtained using the hsCRP assay during the luteal phase, especially for moderate -severe endometriosis. At a cut-off level of hsCRP > 0.71 mg/L, moderate-severe stages were diagnosed with 80.7% sensitivity and 63.9% specificity during the luteal phase. Using a similar cut-off value for CRP analyzed by the classical method, moderate-severe endometriosis was diagnosed with lower sensitivity (67.7%, p = 0.06) and comparable specificity (63.9%).

CONCLUSIONS

The hsCRP assay was superior to the classical CRP assay for the detection of low CRP levels and for revealing subclinical inflammation in plasma of women with endometriosis.

Age-related differences in inflammatory markers in men: contribution of visceral adiposity

As visceral adipose tissue (AT) accumulation and inflammatory markers are known to increase with age, we examined whether this age-related change in regional AT distribution could contribute to the increase in the concentration of some inflammatory markers found with age. Two hundred eight healthy men aged 18.6 to 72.2 years and covering a wide range of adiposity values (body mass index, 18.5-39.3 kg/m(2)) were studied. Plasma C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) levels were measured by enzyme-linked immunosorbent assay. Anthropometric characteristics such as height, weight, and waist girth were measured; and body mass index was calculated. Cross-sectional areas of abdominal AT were obtained at L4-L5 by computed tomography. Fasting blood samples were collected to determine a complete lipoprotein lipid profile, and a 75-g oral glucose tolerance test was performed. Overall, visceral AT accumulation was positively correlated with age (r = 0.51, P < .0001) as well as with plasma CRP (r = 0.39, P < .0001), IL-6 (r = 0.32, P < .0001), and TNF-alpha (r = 0.14, P < .05) levels. A significant positive relationship was also observed between age and CRP (r = 0.36, P < .0001), IL-6 (r = 0.39, P < .0001), or TNF-alpha (r = 0.15, P < .05) concentrations. As middle-aged men were characterized by higher CRP (1.32 [25th percentile, 0.71; 75th percentile, 2.71] vs 0.66 [0.36, 1.62] mg/L, P < .0001) and IL-6 (1.60 [1.09, 2.28] vs 1.12 [0.77, 1.60] pg/mL, P < .0001) levels as well as by a greater amount of visceral AT (P < .0001) than young men, we have individually matched 43 young men (age, 28.6 +/- 5.82 years) with 43 middle-aged men (age, 57.6 +/- 5.15 years) on the basis of their visceral AT. Matching for visceral AT eliminated the difference between middle-aged men and younger adult men in inflammatory markers. These results suggest that the age-related variation in CRP and IL-6 is largely explained by differences in visceral AT.

Effects of consumption of pomegranate juice on carotid intima-media thickness in men and women at moderate risk for coronary heart disease

This randomized, double-blind, parallel trial assessed the influence of pomegranate juice consumption on anterior and posterior carotid intima-media thickness (CIMT) progression rates in subjects at moderate risk for coronary heart disease. Subjects were men (45 to 74 years old) and women (55 to 74 years old) with > or =1 major coronary heart disease risk factor and baseline posterior wall CIMT 0.7 to 2.0 mm, without significant stenosis. Participants consumed 240 ml/day of pomegranate juice (n = 146) or a control beverage (n = 143) for up to 18 months. No significant difference in overall CIMT progression rate was observed between pomegranate juice and control treatments. In exploratory analyses, in subjects in the most adverse tertiles for baseline serum lipid peroxides, triglycerides (TGs), high-density lipoprotein (HDL) cholesterol, TGs/HDL cholesterol, total cholesterol/HDL cholesterol, and apolipoprotein-B100, those in the pomegranate juice group had significantly less anterior wall and/or composite CIMT progression versus control subjects. In conclusion, these results suggest that in subjects at moderate coronary heart disease risk, pomegranate juice consumption had no significant effect on overall CIMT progression rate but may have slowed CIMT progression in subjects with increased oxidative stress and disturbances in the TG-rich lipoprotein/HDL axis.

Sex differences in inflammatory markers: what is the contribution of visceral adiposity?

BACKGROUND

C-reactive protein (CRP) concentrations have been found to be higher in premenopausal women than in men, whereas interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) concentrations have been reported to be lower in women than in men.

OBJECTIVE

The objective was to determine whether the sex difference in body fat distribution accounts for the observed sex differences in inflammatory markers.

DESIGN

Plasma CRP, IL-6, and TNF-alpha concentrations were measured in 208 healthy men (age: 42.2 +/- 15.2 y) and in 145 healthy women (age: 36.8 +/- 11.1 y).

RESULTS

Compared with men, premenopausal women had higher CRP concentrations [1.24 (25th percentile: 0.54; 75th percentile: 3.04) compared with 0.94 (0.51, 2.40) mg/L; P < 0.05] and lower plasma TNF-alpha concentrations [1.50 (25th percentile: 1.23; 75th percentile: 1.82) compared with 1.71 (1.40, 2.05) pg/mL; P < 0.001]. No sex difference in IL-6 concentrations was noted. Regression analyses indicated that the relation between CRP or IL-6 and visceral adipose tissue (VAT) and subcutaneous AT (SAT) was sex-specific; a significantly steeper slope was observed in women than in men (P < 0.05). Sex differences in CRP concentrations were abolished after SAT was adjusted for. In a multivariate model of the whole sample, we found that both SAT and VAT and the sex x SAT interaction term were significant correlates of CRP and IL-6 concentrations. Finally, whereas CRP concentrations were largely influenced by visceral adiposity in men, subcutaneous adiposity was the key correlate of CRP in women.

CONCLUSION

The higher CRP concentrations found in women appear to be due to their greater accumulation of subcutaneous fat than that observed in men.

An integrated microfluidic system for C-reactive protein measurement

This study presents a new microfluidic chip integrated with pneumatic micropumps, normally close microvalves and vortex-type micromixers for C-reactive protein (CRP) measurement. CRP is a protein produced during the inflammation process. It has been reported that CRP in serum can be used for risk assessment of cardiovascular diseases. In this study, CRP measurements were performed by using the integrated microfluidic chip incorporated with magnetic beads. The magnetic beads coated with CRP-specific DNA aptamers were used to recognize, purify and enrich the target CRP. The entire process including sample pre-treatment, and the interaction between the target CRP and anti-CRP antibody was automatically performed on a single chip. The chemiluminescence signal was measured using a luminometer to detect the concentration of CRP afterwards. The entire reaction time is less then 25 min, which is only about 20% of the time required when compared to using traditional bench-top machines (150 min). More importantly, the detection limit has been improved from 0.125 to 0.0125 mg/L with only half the amount of reagent consumption. The development of this microfluidic system is promising for fast, accurate, and sensitive detection of CRP.

Can both EDTA and citrate plasma samples be used in measurements of fibrinogen and C-reactive protein concentrations?

BACKGROUND

Fibrinogen and C-reactive protein (CRP) concentrations are predictors of outcome in the atherosclerotic patient. It is important in risk stratification that these quantities are measured reproducibly in routine and research.

METHOD

In the present study, we compare measurements of fibrinogen and high-sensitivity CRP in EDTA and citrate plasma samples (n=150) using nephelometric immunoassays. Fibrinogen was also measured in citrate plasma using a clotting method.

RESULTS

In approximately one-third of the samples, the fibrinogen concentration measured by immunoassay was higher in citrate plasma than in EDTA plasma, in spite of the dilution by citrate. The immunoassay results of fibrinogen concentration measurements in EDTA and citrate plasma differed significantly and also differed from those of functionally measured fibrinogen concentrations. A difference was found between the concentration of CRP in EDTA plasma and citrated plasma which also did not correspond to the dilution.

CONCLUSIONS

Reproducibility of results is essential in risk stratification by fibrinogen or high-sensitivity CRP concentrations and small differences close to the decision limits may have a decisive impact. Immunological measurements are liable to confounding effects that may be difficult to foresee, qualitatively and quantitatively. Great care should be observed when measuring the concentration of calcium containing analytes in anticoagulated samples. Fibrinogen concentrations should preferably be measured functionally in citrate plasma.

Are C-reactive protein and homocysteine cardiovascular risk factors in obese children and adolescents?

BACKGROUND

Several prospective epidemiological studies have demonstrated that high-sensitivity C-reactive protein (hsCRP) and plasma homocysteine (hcy) are predictors of future coronary events among healthy men and women. The aim of the present study was therefore to investigate a possible relationship between hsCRP, hcy levels and body mass index (BMI), relative weight (RW), serum leptin levels, and cardiovascular risk factors in obese children and adolescents.

METHODS

The study involved 28 obese children and adolescents (13 girls, 15 boys; BMI>95 per thousand for age and sex), 4.5-15 years of age (mean 10.7 +/- 0.6 years), who attended hospital for a basic obesity check-up. The association between hsCRP, hcy levels and BMI, RW, serum leptin levels, and cardiovascular risk factors such as blood pressure (BP), lipid profile, serum fasting insulin levels, and insulin resistance indexes, was investigated.

RESULTS

Serum hsCRP level was positively correlated with BMI (r = 0.512, P < 0.01), RW (r = 0.438, P < 0.05), systolic and diastolic BP (r = 0.498, P < 0.01), serum leptin levels (r = 0.457, P < 0.05), but not with serum lipid, glucose, fasting insulin, plasma hcy levels or insulin resistance indexes. For hcy level, in contrast, no correlation was found with BMI, RW, systolic and diastolic BP, serum lipid levels, leptin, hsCRP, glucose, fasting insulin levels, or insulin resistance indexes.

CONCLUSIONS

hsCRP is correlated with BMI, RW, BP and leptin, which are risk factors for coronary heart disease, which supports the relationship between obesity, inflammation and atherosclerosis. hsCRP in childhood obesity might be a useful index to predict possible atherosclerotic events.

Visceral adipose tissue and the ratio of visceral to subcutaneous adipose tissue are greater in adults with than in those without spinal cord injury, despite matching waist circumferences

BACKGROUND

Abdominal obesity, particularly visceral adipose tissue (VAT), is associated with an increased risk of coronary heart disease (CHD). Despite an elevated risk of CHD mortality in persons with spinal cord injury (SCI), neither abdominal adipose tissue accumulation nor the validity of waist circumference (WC) has been determined in persons with SCI.

OBJECTIVES

The objectives of this study were to compare total adipose tissue (TAT), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and the ratio of VAT to SAT (VAT:SAT) between adults with SCI and age-, sex-, and WC-matched able-bodied (AB) controls and to determine the relation between WC and VAT in both groups.

DESIGN

Thirty-one men and women (n = 15 SCI and 16 AB) with a mean (+/-SD) age of 38.9 +/- 7.9 y participated in this cross-sectional study. Abdominal adipose tissue was quantified by computed tomography at L4-L5. WC was measured at 3 sites: lowest rib, iliac crest, and the midpoint between the lowest rib and iliac crest.

RESULTS

Persons with SCI had a 58% greater mean VAT (P = 0.003), 48% greater mean VAT:SAT (P = 0.034), and 26% greater mean TAT (P = 0.055) than did matched AB controls after differences in weight were accounted for. Mean SAT was not significantly different between groups. WC at all sites was correlated with VAT in both groups (SCI: 0.905 < or = r < or = 0.925; AB: 0.838 < or = r < or = 0.877; both P < 0.001).

CONCLUSIONS

High levels of VAT exist in young people with SCI who classify themselves as active and healthy. WC may be a valid surrogate measure of VAT in this population and serve as a tool for clinicians to identify those at risk of CHD.

An overview of inflammatory markers in type 2 diabetes from the perspective of the clinical chemist

C-reactive protein (CRP), when measured by a highly sensitive method, is a measure of lowgrade, chronic inflammation and is an independent risk factor for type 2 diabetes (T2D) and cardiovascular disease (CVD). CRP also has the capacity to interact with other risk factors to increase the risk for T2D and CVD. Population distributions divided into tertiles provide the capacity to predict onset of T2D and associated CVD. Preanalytical as well as analytical sources of variation in high-sensitivity CRP (hsCRP) measurements need to be standardized in order for CRP results to be optimally useful. The Centers for Disease Control and Prevention and the American Heart Association have issued guidelines for clinical usefulness of hsCRP measurements. The Centers for Disease Control and Prevention has taken steps to standardize hsCRP assays by evaluating secondary reference materials to be used by manufacturers to calibrate their assays.

Immunodetection of pentamer and modified C-reactive protein using surface plasmon resonance biosensing

In clinical practices, the examination of pentamer C-reactive protein (pCRP) is commonly used as a prognostic indicator of the risk of a patient developing cardiovascular disease (CVD). Structural modification of pCRP produces a modified CRP (mCRP) which exhibits different biological activities in the body. In recent years, mCRP has come to be regarded as a more powerful inducer than pCRP, and hence mCRP measurement has emerged as an important indicator for assessing the risk of developing CVD. The surface plasmon resonance (SPR) biosensing technique can be employed to increase the detection accuracy and real-time response when sensing pCRP or mCRP. In this study, three monoclonal antibodies (Mabs), C8, 8D8, and 9C9, are immobilized on a protein G layer for subsequent CRP detection. The experimental results reveal that the Mab C8 reacts with both pCRP and mCRP, the Mab 8D8 with pCRP, and the Mab 9C9 with mCRP. No false signals caused by non-specific binding are observed. When detecting pCRP using Mab C8, the SPR bioassay provides sufficient sensitivity to evaluate whether or not a patient is at risk of developing CVD. SPR biosensing provides a viable and accurate approach for the real-time evaluation of pCRP and mCRP levels, and is therefore of considerable benefit in clinical examinations of CPR.

Association between novel indices of malnutrition-inflammation complex syndrome and cardiovascular disease in hemodialysis patients

BACKGROUND

Inflammation and malnutrition are recognized as important risk factors for cardiovascular disease (CVD) in hemodialysis (HD) patients. Owing to substantial short-term variability of serum C-reactive protein (CRP), more reliable markers of malnutrition-inflammation complex syndrome should be sought with stronger associations with the risk of CVD in HD patients. We therefore explored the clinical relevance of a composite inflammatory index (prognostic inflammatory and nutritional index [PINI]) and of muscle protein mass indicators, derived from creatinine kinetics.

METHODS

This cross-sectional study included 177 HD patients (89 women and 88 men; median age, 67.73 years). CVD and risk factors were assessed using medical charts, clinical examination, and biochemical measurements performed at inclusion. Lean body mass (LBM) was derived from creatinine kinetic modeling, whereas PINI was calculated as the ratio (CRP xalpha1-acid-glycoprotein)/(albumin x transthyretin). Patients were divided according to the presence or absence of established CVD.

RESULTS

The traditional risk factors diabetes (odds ratio [OR], 5.83; p = 0.0045) and smoking (OR, 3.50; p < 0.02) were associated with an increase in prevalent CVD. Low transthyretin (OR, 3.79; p < 0.02) and high levels of CRP (OR, 2.70; p < 0.05), PINI (OR, 3.44; p < 0.02), observed LBM (OR, 3.01; p < 0.05), and the ratio of observed/expected LBM (OR, 4.24; p < 0.01) were associated with CVD after adjustment for age, sex, dialysis center, and dialysis vintage. After additional adjustment for diabetes and smoking, only PINI (OR, 2.85; p = 0.0446) and observed/expected LBM (OR, 2.96; p = 0.0361) were still significant.

CONCLUSION

PINI and LBM are associated with increased relative risk for having CVD and could be used routinely to examine the degree of severity of malnutrition inflammation complex syndrome.

Analytical performance of the Synchron LX®20 Pro, BN™II and IMMAGE® high sensitivity C-reactive protein assays and concordance in cardiovascular risk stratification

BACKGROUND

C-reactive protein (CRP) can provide valuable prognostic information for risk of cardiovascular events. Several automated high sensitivity CRP immunoassays are currently available for risk assessment.

METHODS

The analytical performance of the Synchron LX20 Pro, BN II and IMMAGE high sensitivity CRP assays were evaluated and concordance within cardiovascular risk tertiles was examined for 529 serum samples.

RESULTS

All three assays exhibited satisfactory between-run imprecision based on CVs< or =9.0% over a wide range of CRP concentrations. The LX20 Pro and BN II were linear over an extensive measuring range, whereas the IMMAGE exhibited a slight deviation from linearity producing results with a positive bias at CRP levels between 0.7 and 2.6 mg/l. Moderately hemolyzed samples interfered with the LX20 Pro and IMMAGE CRP assays, whereas moderate lipemia interfered with the BN II. Correlation studies revealed that the LX20 Pro and IMMAGE produced results 8.2% lower and 5.1% lower, respectively, compared with the BN II. There was good agreement among methods for cardiovascular risk assessment.

CONCLUSIONS

All three CRP assays exhibited acceptable analytical performance for cardiovascular risk assessment. Although results by the LX20 Pro and IMMAGE were lower than the BN II, there was good agreement within each cardiovascular risk assessment tertile.

Immunoturbidimetric determination of C-reactive protein (CRP) and high-sensitivity CRP on heparin plasma. Comparison with serum determination

Determination of C-reactive protein (CRP) and high-sensitivity CRP (hs-CRP), markers of systemic inflammation and atherosclerosis risk, usually requires serum samples, while heparin plasma samples are routinely collected for routine chemistry. This study evaluates the use of heparin plasma samples for hs-CRP and CRP determinations using immunoturbidimetric methods on an Olympus system. As a result, analytical performance, including linearity, imprecision values, and determination from 185 clinical samples, are not affected by the type of sampling, validating the use of heparin plasma samples for CRP and hs-CRP determination with Olympus reagents.

Inflammatory markers and coronary heart disease

PURPOSE OF REVIEW

Despite changes in lifestyle and the use of effective pharmacologic interventions to lower cholesterol levels, coronary heart disease remains the major cause of morbidity and mortality in the developed world. Cholesterol screening fails to identify almost 50% of those individuals who will present with acute coronary syndromes. Recent evidence from laboratory and prospective clinical studies demonstrates that atherosclerosis is not simply a disease of lipid deposition, but rather is an inflammatory process with highly specific cellular and molecular responses. The clinical utility of inflammatory markers has been examined in a variety of atherothrombotic diseases. Because C-reactive protein is highly stable in stored frozen samples, and automated and robust analytical systems for its measurement are available, it has become the most widely examined inflammatory marker.

RECENT FINDINGS

C-reactive protein has consistently been shown to be a useful prognostic indicator in acute coronary syndromes and is a strong predictor of future coronary events in apparently healthy individuals. In addition, C-reactive protein can identify individuals with normal lipid levels who are at increased risk for future coronary events. Because drugs such as aspirin and statins reduce inflammatory risk, C-reactive protein has the potential to guide the use of these therapies in high-risk individuals for primary prevention.

SUMMARY

C-reactive protein may have a role in global risk assessment for primary prevention and in targeting those patients who will benefit from anti-inflammatory therapies. In addition, it may also be a good prognostic indicator in patients with acute coronary syndromes.

Development of immunoturbidimetric assays for fourteen human serum proteins on the Hitachi 912

Many laboratories rely on dedicated nephelometers or turbidimeters and commercial reagent kits for the evaluation of serum proteins. However, with growing emphasis on cost containment, laboratories are forced to seek additional operational efficiencies by capitalizing on the use of existing analyzers whenever possible. In the present paper we describe the development of immunoturbidimetric assays for routine analysis of 14 human serum proteins (alpha1-antitrypsin, alpha2-macroglobulin, albumin, apolipoproteins Al and B, complement components 3 and 4, haptoglobin, immunoglobulins A, G, and M, orosomucoid, prealbumin, and transferrin) on the Hitachi 912, a general chemistry analyzer. With this system, we obtained excellent precision at levels corresponding to low, normal, and high physiologic concentrations of each protein (within-run imprecision CVs < or = 3.4%, total imprecision CVs < or = 4.1%). Linearity for each method was within 5% of the expected value throughout the calibration range, and method comparisons with either the Roche turbidimetric or Dade Behring nephelometric assays were in good agreement (r >0.97). We observed no significant interference from bilirubin (up to 718 micromol/l), hemoglobin (up to 8 g/l), triglyceride (up to 14.7 mmol/l) or rheumatoid factor (up to 4,140 IU/ml). Calibration for the 14 protein assays was stable for at least 7 days and onboard refrigerated reagents were stable for at least 3 months. The instrument's automated sample re-run feature minimized sample handling and helped to conserve specimens. In conclusion, the newly developed assays on the Hitachi 912 offer high throughput (>250 tests per hour) without the associated cost of a dedicated instrument for protein assays.