Comparison of the Diagnostic Accuracy of Brain Natriuretic Peptide (BNP) and the N-Terminal Part of the Propeptide of BNP Immunoassays in Chronic and Acute Heart Failure: A Systematic Review

NT-ProBNP levels in saliva and its clinical relevance to heart failure

Background

Current blood based diagnostic assays to detect heart failure (HF) have large intra-individual and inter-individual variations which have made it difficult to determine whether the changes in the analyte levels reflect an actual change in disease activity. Human saliva mirrors the body’s health and well being and ∼20% of proteins that are present in blood are also found in saliva. Saliva has numerous advantages over blood as a diagnostic fluid which allows for a non-invasive, simple, and safe sample collection. The aim of our study was to develop an immunoassay to detect NT-proBNP in saliva and to determine if there is a correlation with blood levels.

Methods

Saliva samples were collected from healthy volunteers (n = 40) who had no underlying heart conditions and HF patients (n = 45) at rest. Samples were stored at −80°C until analysis. A customised homogeneous sandwich AlphaLISA^(R) immunoassay was used to quantify NT-proBNP levels in saliva.

Results

Our NT-proBNP immunoassay was validated against a commercial Roche assay on plasma samples collected from HF patients (n = 37) and the correlation was r² = 0.78 (p<0.01, y = 1.705× +1910.8). The median salivary NT-proBNP levels in the healthy and HF participants were <16 pg/mL and 76.8 pg/mL, respectively. The salivary NT-proBNP immunoassay showed a clinical sensitivity of 82.2% and specificity of 100%, positive predictive value of 100% and negative predictive value of 83.3%, with an overall diagnostic accuracy of 90.6%.

Conclusion

We have firstly demonstrated that NT-proBNP can be detected in saliva and that the levels were higher in heart failure patients compared with healthy control subjects. Further studies will be needed to demonstrate the clinical relevance of salivary NT-proBNP in unselected, previously undiagnosed populations.

Multimarker strategy for short-term risk assessment in patients with dyspnea in the emergency department: the MARKED (Multi mARKer Emergency Dyspnea)-risk score

OBJECTIVES

The study aim was to determine the prognostic value of a multimarker strategy for risk-assessment in patients presenting to the emergency department (ED) with dyspnea.

BACKGROUND

Combining biomarkers with different pathophysiological backgrounds may improve risk stratification in dyspneic patients in the ED.

METHODS

The study prospectively investigated the prognostic value of the biomarkers N-terminal pro-B-type natriuretic peptide (NT-proBNP), high-sensitivity cardiac troponin T (hs-cTnT), Cystatin-C (Cys-C), high-sensitivity C-reactive protein (hs-CRP), and Galectin-3 (Gal-3) for 90-day mortality in 603 patients presenting to the ED with dyspnea as primary complaint.

RESULTS

hs-CRP, hs-cTnT, Cyst-C, and NT-proBNP were independent predictors of 90-day mortality. The number of elevated biomarkers was highly associated with outcome (odds ratio: 2.94 per biomarker, 95% confidence interval [CI]: 2.29 to 3.78, p < 0.001). A multimarker approach had incremental value beyond a single-marker approach. Our multimarker emergency dyspnea-risk score (MARKED-risk score) incorporating age ≥75 years, systolic blood pressure <110 mm Hg, history of heart failure, dyspnea New York Heart Association functional class IV, hs-cTnT ≥0.04 μg/l, hs-CRP ≥25 mg/l, and Cys-C ≥1.125 mg/l had excellent prognostic performance (area under the curve: 0.85, 95% CI: 0.81 to 0.89), was robust in internal validation analyses and could identify patients with very low (<3 points), intermediate (≥3, <5 points), and high risk (≥5 points) of 90-day mortality (2%, 14%, and 44% respectively; p < 0.001).

CONCLUSIONS

A multimarker strategy provided superior risk stratification beyond any single-marker approach. The MARKED-risk score that incorporates hs-cTnT, hs-CRP, and Cys-C along with clinical risk factors accurately identifies patients with very low, intermediate, and high risk.

Association of natriuretic peptide receptor-C gene with ischemic stroke and hypertension in Chinese Han population

To investigate whether natriuretic peptide receptor-C (NPR3) gene polymorphisms were associated with ischemic stroke (IS) and hypertension (a conventional risk factor for stroke), we conducted a case-control study in Chinese Han population. We found that rs696831, located in intron 2, was associated with IS. In addition, we found that rs16890208 and rs700925, in linkage disequilibrium (LD) with each other in intron 3, were associated with hypertension. The A allele of the rs16890208, T allele of the rs700925, and the AT haplotype, derived from rs16890208 and rs700925, increased the risk of hypertension with odds ratios (ORs) of 1.74 (95% CI = 1.23-2.47), 1.72 (95% CI = 1.21-2.42), and 1.54 (95% CI = 1.14-2.08), respectively. Further, we found that rs11745562 and rs2270915, in LD with each other in intron 5 and exon 8, were associated with hypertension. The A allele of the rs11745562 and the G allele of the rs2270915 increased the risk of hypertension with ORs of 1.53 (95% CI = 1.07-2.19) and 1.55 (95% CI = 1.08-2.22), respectively. Therefore, we provided novel evidences that polymorphisms or haplotype in NPR3 gene may influence the risk of IS or hypertension independently in Chinese population.

Classification of heart failure in the atherosclerosis risk in communities (ARIC) study: a comparison of diagnostic criteria

BACKGROUND

Population-based research on heart failure (HF) is hindered by lack of consensus on diagnostic criteria. Framingham (FRM), National Health and Nutrition Examination Survey (NHANES), Modified Boston (MBS), Gothenburg (GTH), and International Classification of Disease, 9th Revision, Clinical Modification (ICD-9-CM) code criteria, do not differentiate acute decompensated heart failure (ADHF) from chronic stable HF. We developed a new classification protocol for identifying ADHF in the Atherosclerosis Risk in Communities (ARIC) Study and compared it with these other schemes.

METHODS AND RESULTS

A sample of 1180 hospitalizations with a patient address in 4 study communities and eligible discharge codes were selected. After assessing whether the chart contained evidence of possible HF signs, 705 were fully abstracted. Two independent reviewers classified each case as ADHF, chronic stable HF, or no HF, using ARIC classification guidelines. Fifty-nine percent of cases met ARIC criteria for ADHF and 13.9% and 27.1% were classified as chronic stable HF or no HF, respectively. Among events classified as HF by FRM criteria, 68.4% were validated as ADHF, 9.6% as chronic stable HF, and 21.9% as no HF. However, 92.5% of hospitalizations with a primary ICD-9-CM 428 "heart failure" code were validated as ADHF. Sensitivities of comparison criteria to classify ADHF ranged from 38-95%, positive predictive values from 62-92%, and specificities from 19-96%.

CONCLUSIONS

Although comparison criteria for classifying HF were moderately sensitive in identifying ADHF, specificity varied when applied to a randomly selected set of suspected HF hospitalizations in the community.

Clinical Use of Natriuretic Peptides

Either B-type natriuretic peptide (BNP) or NT-proBNP may be used as a diagnostic, screening, prognostic and therapeutic tool for CHF. The Food and Drug Administration (FDA) cleared the cut-off point for BNP at 100 pg/mL, and that of NT-proBNP at 125 pg/mL for patients <75 years and 450 pg/mL for those >75. A steadily rising titre even below the cut-off value should be raised as a concern as heart failure is progressive if left untreated and may result in cardiac death. Both biomarkers are also featured in lab investigations for patients with acute coronary syndrome (ACS).

Brain natriuretic peptide between traditional and nontraditional risk factors in hemodialysis patients: analysis of cardiovascular mortality in a two-year follow-up

BACKGROUND

The ability of brain natriuretic peptide (BNP) together with other traditional and nontraditional risk factors to predict cardiovascular (CV) mortality in hemodialysis (HD) patients has not been well established. The aim of this prospective study was to determine the predictive cutoff values of baseline measurement of BNP along with the known CV disease risk factors to predict all-cause and CV mortality in HD patients.

METHODS

BNP concentration before HD was measured in 125 prevalent HD patients (age 53.0 ± 13.5 years, HD vintage 75.2 ± 61.0 months). In addition, several traditional CV risk factors (blood pressure, dyslipidemia, diabetes mellitus, body mass index, left ventricular hypertrophy) and uremia/dialysis-related CV risk factors (anemia, calcium and phosphate impairment, malnutrition, inflammation, ultrafiltration, HD duration, Kt/V) were examined.

RESULTS

During the 2-year follow-up, we lost 28 out of 125 patients (22.5%), with CV disease (65.7%) being the main cause of mortality. The cutoff point for BNP, as predictor of the clinical outcome, according to the ROC curve was 1,194 pg/ml for CV mortality with sensitivity and specificity of 63 and 65%, respectively (AUC 0.61 and confidence interval (CI) 95% 0.47-0.75). Kaplan-Meier analysis showed that all-cause (log-rank, p = 0.002) and CV mortality (log-rank, p = 0.001) were the cause of a significantly lower survival in patients with a mean BNP >1,200 pg/ml. The univariate Cox regression analysis found the following factors to be predictors of all-cause mortality: hemoglobin (<110 g/l), phosphorus (>1.78 mmol/l), albumin (<40 g/l), C-reactive protein (CRP ≥ 10 mg/l), BNP (>1,200 pg/ml) and cardiac ejection fraction (≤ 55%). The multivariate Cox regression analyses demonstrated that only CRP ≥ 10 mg/l with a hazard ratio (HR) 6.82 (CI 95% 1.86-24.9, p = 0.004) and BNP >1,200 pg/ml with HR 5.79 (CI 95% 1.58-21.3, p = 0.004) were predictors of all-cause mortality. BNP >1,200 pg/ml with HR 13.52 (CI 95% 1.68-108.9, p = 0.014) was found to be an even stronger predictor of CV mortality than CRP ≥ 10 mg/l with HR 6.53 (CI 95% 1.35-31.6, p = 0.020).

CONCLUSIONS

Our study pointed out that BNP >1,200 pg/ml as a marker of cardiac dysfunction and CRP ≥ 10 mg/l as a marker of inflammation identify HD patients at increased risk of CV mortality.

The effect of the brain-type natriuretic peptide single-nucleotide polymorphism rs198389 on test characteristics of common assays

OBJECTIVE

To assess in a US general adult population the effect of the functional single-nucleotide polymorphism rs198389 in the promoter region of the gene of brain-type natriuretic peptide (BNP) on 3 commonly used BNP assays, clinical phenotype, disease prevalence, overall survival, and diagnostic test characteristics of BNP as a biomarker.

PATIENTS AND METHODS

We genotyped for rs198389 in a random sample of the general population (aged ≥ 45 years; n = 1970; enrolled between June 1, 1997, and September 30, 2000) from Olmsted County, Minnesota. Patients were characterized biochemically, clinically, echocardiographically, and regarding BNP molecular forms (2 assays for BNP and 1 assay for amino-terminal proBNP). Median follow-up was 9 years.

RESULTS

Genotype frequencies were in Hardy-Weinberg equilibrium (P = .98): TT genotype, n = 645 (32.7%); TC genotype, n = 983 (49.9%); and CC genotype, n = 342 (17.4%). The C allele independently predicted higher BNP forms (P<.001 for all assays). Genotypes did not differ with regard to clinical and echocardiographic phenotype or overall survival. When previously reported genotype-unadjusted cut points for the detection of left ventricular ejection fraction less than or equal to 40% (n = 37 [1.9%]) and less than or equal to 50% (n = 116 [6.0%]) were used, sensitivity generally increased with the number of C alleles, whereas specificity decreased, both on average by more than 10% for the TT vs CC genotype.

CONCLUSION

The C allele of rs198389 is common in the general US population and is associated with higher concentrations of BNP molecular forms but not with cardiovascular phenotype or survival. The C allele confounds the test characteristics of commonly used assays.

Genome-wide association analysis and fine mapping of NT-proBNP level provide novel insight into the role of the MTHFR-CLCN6-NPPA-NPPB gene cluster

High blood concentration of the N-terminal cleavage product of the B-type natriuretic peptide (NT-proBNP) is strongly associated with cardiac dysfunction and is increasingly used for heart failure diagnosis. To identify genetic variants associated with NT-proBNP level, we performed a genome-wide association analysis in 1325 individuals from South Tyrol, Italy, and followed up the most significant results in 1746 individuals from two German population-based studies. A genome-wide significant signal in the MTHFR-CLCN6-NPPA-NPPB gene cluster was replicated, after correction for multiple testing (replication one-sided P-value = 8.4 × 10⁻¹⁰). A conditional regression analysis of 128 single-nucleotide polymorphisms in the region of interest identified novel variants in the CLCN6 gene as independently associated with NT-proBNP. In this locus, four haplotypes were associated with increased NT-proBNP levels (haplotype-specific combined P-values from 8.3 × 10⁻⁰³ to 9.3 × 10⁻¹¹). The observed increase in the NT-proBNP level was proportional to the number of haplotype copies present (i.e. dosage effect), with an increase associated with two copies that varied between 20 and 100 pg/ml across populations. The identification of novel variants in the MTHFR-CLCN6-NPPA-NPPB cluster provides new insights into the biological mechanisms of cardiac dysfunction.

Direct comparison of serial B-type natriuretic peptide and NT-proBNP levels for prediction of short- and long-term outcome in acute decompensated heart failure

Introduction

Monitoring treatment efficacy and assessing outcome by serial measurements of natriuretic peptides in acute decompensated heart failure (ADHF) patients may help to improve outcome.

Methods

This was a prospective multi-center study of 171 consecutive patients (mean age 80 73-85 years) presenting to the emergency department with ADHF. Measurement of BNP and NT-proBNP was performed at presentation, 24 hours, 48 hours and at discharge. The primary endpoint was one-year all-cause mortality; secondary endpoints were 30-days all-cause mortality and one-year heart failure (HF) readmission.

Results

During one-year follow-up, a total of 60 (35%) patients died. BNP and NT-proBNP levels were higher in non-survivors at all time points (all P < 0.001). In survivors, treatment reduced BNP and NT-proBNP levels by more than 50% (P < 0.001), while in non-survivors treatment did not lower BNP and NT-proBNP levels. The area under the ROC curve (AUC) for the prediction of one-year mortality increased during the course of hospitalization for BNP (AUC presentation: 0.67; AUC 24 h: 0.77; AUC 48 h: 0.78; AUC discharge: 0.78) and NT-proBNP (AUC presentation: 0.67; AUC 24 h: 0.73; AUC 48 h: 0.75; AUC discharge: 0.77). In multivariate analysis, BNP at 24 h (1.02 [1.01-1.04], P = 0.003), 48 h (1.04 [1.02-1.06], P < 0.001) and discharge (1.02 [1.01-1.03], P < 0.001) independently predicted one-year mortality, while only pre-discharge NT-proBNP was predictive (1.07 [1.01-1.13], P = 0.016). Comparable results could be obtained for the secondary endpoint 30-days mortality but not for one-year HF readmissions.

Conclusions

BNP and NT-proBNP reliably predict one-year mortality in patients with ADHF. Prognostic accuracy of both biomarker increases during the course of hospitalization. In survivors BNP levels decline more rapidly than NT-proBNP levels and thus seem to allow earlier assessment of treatment efficacy. Ability to predict one-year HF readmission was poor for BNP and NT-proBNP.

Trial registration

ClinicalTrials.gov identifier: NCT00514384.

Processing of pro-B-type natriuretic peptide: furin and corin as candidate convertases

BACKGROUND

B-type natriuretic peptide (BNP) and its N-terminal fragment (NT-proBNP) are the products of the enzyme-mediated cleavage of their precursor molecule, proBNP. The clinical significance of proBNP-derived peptides as biomarkers of heart failure has been explored thoroughly, whereas little is known about the mechanisms of proBNP processing. We investigated the role of 2 candidate convertases, furin and corin, in human proBNP processing.

METHODS

We measured proBNP expression in HEK 293 and furin-deficient LoVo cells. We used a furin inhibitor and a furin-specific small interfering RNA (siRNA) to explore the implication of furin in proBNP processing. Recombinant proBNPs were incubated with HEK 293 cells transfected with the corin-expressing plasmid. We applied mass spectrometry to analyze the products of furin- and corin-mediated cleavage.

RESULTS

Reduction of furin activity significantly impaired proBNP processing in HEK 293 cells. Furin-deficient LoVo cells were unable to process proBNP, whereas coexpression with furin resulted in effective proBNP processing. Mass spectrometric analysis revealed that the furin-mediated cleavage of proBNP resulted in BNP 1-32, whereas corin-mediated cleavage led to the production of BNP 4-32. Some portion of proBNP in the plasma of heart failure patients was not glycosylated in the cleavage site region and was susceptible to furin-mediated cleavage.

CONCLUSIONS

Both furin and corin are involved in the proBNP processing pathway, giving rise to distinct BNP forms. The significance of the presence of unprocessed proBNP in circulation that could be cleaved by the endogenous convertases should be further investigated for better understanding BNP physiology.

Point-of-care testing for cardiac markers in acute coronary syndromes and heart failure

Advances in technologies for immunoassay testing have enabled the development of 15-minute whole-blood assays for cardiac markers in the evaluation of patients with acute coronary syndromes (ACS) and congestive heart failure. In many cases, the analytical performance of these assays is equivalent to that of testing in the central laboratory. Rapid whole-blood point-of-care assays for troponin, creatine kinase isoenzyme CK-MB, myoglobin, and B-type natriuretic peptides have facilitated efforts to restructure conventional approaches to ACS and heart failure in the emergency room. Improvements in outcomes, including decreased emergency room and hospital length-of-stay, decreased overall cost, and earlier discharge of low-risk patients, have been documented following implementation of these technologies.

The response of circulating brain natriuretic peptide to academic stress in college students

Brain natriuretic peptide (BNP), a cardiac peptide, has been implicated in the regulation of hypothalamic-pituitary-adrenocortical (HPA) responses to psychological stressors. The influence of academic stress on circulating concentration of the N-terminal fragment of BNP precursor (NT-proBNP), and in relation to the stress hormone (cortisol) response was studied in 170 college students undergoing major examinations. Just prior to the examination, we measured self-estimated stress level, systolic, and diastolic blood pressure (SBP, DBP), heart rate (HR), plasma levels of cortisol, and NT-proBNP. These parameters were compared to the participants' baseline measurements, taken at the same hour of a different 'control day', without a major examination to induce stress. Hemodynamic variables (SBP, DBP, and HR) increased on the examination day compared with baseline values ( p < 0.001). Circulating cortisol concentration increased before examinations (+42%, p < 0.001). The response to stress was marked by a significant decrease in plasma NT-proBNP concentration (-40%, p < 0.001). We found in males a significant interaction between the cortisol elevation with examination stress and the NT-proBNP reduction ( p = 0.02). In response to academic stress, the plasma cortisol elevation was accompanied by a marked reduction in plasma NT-proBNP level. These data may indicate that mental stress entails an interface between the HPA axis and the peripheral natriuretic peptide system, leading to reciprocating changes in circulating levels of the corresponding hormones.

Usefulness of serum N-terminal-ProBNP in distinguishing ascites due to cirrhosis from ascites due to heart failure

BACKGROUND

Ascites due to cirrhosis may be difficult to distinguish from ascites due to heart failure by clinical features alone. More invasive testing is usually necessary, such as measurement of the hepatic venous pressure gradient, or paracentesis with measurement of the ascitic fluid total protein.

AIM

The aim of this study is to determine the diagnostic accuracy of serum NT-proBNP (N-terminal-pro-brain-type natriuretic peptide) in distinguishing patients with ascites from heart failure or cirrhosis.

METHODS

Using a bank of previously collected fluid, we measured the serum and ascitic NT-proBNP levels in 58 patients with known cirrhosis, and 18 patients with known heart failure. Patients with both disease processes were excluded. The total protein levels in ascites was also measured and compared with serum NT-proBNP levels.

RESULTS

The median serum NT-proBNP level was 165.7 pg/mL (range, 29.9 to 1795) in the cirrhosis group and 6100 pg/mL (range, 1110 to 116,248) in the heart failure group (P<0.001). Similar values were also found when using ascitic fluid NT-proBNP levels. Using a value of 1000 pg/mL, the sensitivity of serum NT-proBNP in ruling out cirrhosis as the cause for ascites was 100%.

CONCLUSIONS

Serum NT-proBNP seems to be an extremely powerful marker in distinguishing ascites due to cirrhosis from ascites due to heart failure. Serum NT-proBNP may potentially replace the more invasive testing presently in use.

Comparison of midregional pro-atrial natriuretic peptide with N-terminal pro-B-type natriuretic peptide in the diagnosis of heart failure

OBJECTIVES

The concentration of atrial natriuretic peptide (ANP) in the circulation is approximately 10- to 50- fold higher than B-type natriuretic peptide (BNP). We sought to compare the accuracy of midregional pro-atrial natriuretic peptide (MRproANP) measured with a novel sandwich immunoassay with N-terminal pro-B-type natriuretic peptide (NTproBNP) in the diagnosis of heart failure.

DESIGN

The diagnosis of heart failure was adjudicated by two independent cardiologists using all available clinical data (including BNP levels) in 287 consecutive patients presenting with dyspnoea to the emergency department (ED). MRproANP and NTproBNP levels were determined at presentation in a blinded fashion.

RESULTS

Heart failure was the adjudicated final diagnosis in 154 patients (54%). Median MRproANP was significantly higher in patients with heart failure as compared to patients with other causes of dyspnoea (400 vs. 92 pmol L(-1), P < 0.001). The diagnostic accuracy of MRproANP was very high with an area under the receiver operating characteristic curve of 0.92 and was comparable with that of NTproBNP (0.92, P = 0.791). Moreover, MRproANP provided incremental diagnostic information to BNP and NTproBNP in patients presenting with BNP levels in the grey zone between 100 and 500 pg mL(-1).

CONCLUSION

Midregional pro-atrial natriuretic peptide is as accurate in the diagnosis of heart failure as NTproBNP. MRproANP seems to provide incremental information on top of BNP or NT-proBNP in some subgroups and should be further investigated in other studies.

Natriuretic peptides in the diagnosis and management of chronic heart failure

Circulating levels of the BNP system can help in the diagnosis of cardiovascular disease and provide prognostic information not only for patients who have HF but also for the general population and other patient groups. Changes over time also carry prognostic information, and studies are assessing BNP-guided treatment strategies. With the identification of circulating molecular forms of BNP, new insights regarding the biology of the BNP system are emerging that may improve the diagnostic and prognostic value of BNP. Likewise, accounting for rs198389 (a common single nucleotide polymorphism that increases BNP levels) may help to further refine the use of components of the BNP system as biomarkers.

Comparison of the cardiac markers B-type natriuretic peptide and N-terminal pro B-type natriuretic peptide

B-type natriuretic peptide and N-terminal pro B-type natriuretic peptide have emerged as powerful biomarkers for heart failure and other cardiovascular conditions. B-type natriuretic peptide and N-terminal pro B-type natriuretic peptide are synthesized on the basis of myocardial stress and hypertrophy and are detectable in serum by several commercially available assays. Although both markers display wide similarities in their predictive values for acute and chronic heart failure, important differences exist regarding cutoff values and influence of noncardiac variables. The similarities and differences between B-type natriuretic peptide and N-terminal pro B-type natriuretic peptide will be reviewed and illustrated in detail regarding preanalytics and analytics, predictive properties for acute and chronic heart failure and prognosis as well as the influence of noncardiac parameters.

Chromogranin-A and N-terminal pro-brain natriuretic peptide: an excellent pair of biomarkers for diagnostics in patients with neuroendocrine tumor

PURPOSE

For the last decade chromogranin-A (CgA) has been a well-established marker for neuroendocrine tumor (NET), and N-terminal pro-brain natriuretic peptide (NT-proBNP) has been a useful marker for left ventricular dysfunction. This study examined the diagnostic value of CgA and NT-proBNP for carcinoid heart disease (CHD), and their prognostic value for overall survival in NET patients.

PATIENTS AND METHODS

Serum samples were obtained and cardiac ultrasound studies performed in 102 NET patients. The criterion for mild and severe CHD was tricuspid regurgitation stage I/II and III/IV, respectively. Proportional odds and Cox proportional hazards models were constructed respectively to identify the association between CHD and overall survival with patient characteristics and the two markers.

RESULTS

Severe CHD was found in 15 (15%) of 102 patients, 13 of whom had elevated NT-proBNP levels. In the univariate proportional odds model CHD was correlated with age (P = .007), CgA (P = .002), and NT-proBNP (P < .001), whereas in the multivariate model NT-proBNP and CgA were significantly associated with CHD (P < .001 and P = .01). In the univariate Cox models, age (P = .04), sex (P = .03), CgA (P = .003), and NT-proBNP (P = .04) were related to overall survival, and in the multivariate model CgA and NT-proBNP remained significantly related to overall survival (P = .002 and P = .04, respectively).

CONCLUSION

NT-proBNP and CgA are very important markers in the diagnosis of CHD in patients with NET. Furthermore, patients with elevated NT-proBNP in addition to elevated CgA levels showed worse overall survival than patients with elevated CgA alone.

Impact of Left Ventricular End-Diastolic Wall Stress on Plasma B-Type Natriuretic Peptide in Heart Failure with Chronic Kidney Disease and End-Stage Renal Disease

Background: Plasma B-type natriuretic peptide (BNP) is a diagnostic and prognostic marker in heart failure (HF). Although renal function is reported as an important clinical determinant, precise evaluations of the relationships of renal function with hemodynamic factors in determining BNP have not been performed. Therefore, we evaluated the association of plasma BNP concentrations with LV end-diastolic wall stress (EDWS) in a broad range of HF patients including those with chronic kidney disease (CKD) and end-stage renal disease (ESRD).

Methods: In 156 consecutive HF patients including those with CKD and ESRD, we measured plasma BNP and performed echocardiography and cardiac catheterization. LV EDWS was calculated as a crucial hemodynamic determinant of BNP.

Results: Plasma BNP concentrations increased progressively with decreasing renal function across the groups (P &lt; 0.01) and were correlated with LV EDWS (r = 0.47) in the HF patients overall. This relationship was also present when patients were subdivided into systolic and diastolic HF (P &lt; 0.01). In multivariable analysis, higher EDWS was associated with increased BNP concentration independently of renal dysfunction (P &lt; 0.01). Anemia, systolic HF, and decreased BMI also contributed to increased BNP concentrations.

Conclusions: These results suggest that LV EDWS is a strong determinant of BNP even in patients with CKD and ESRD. Anemia, obesity, and HF type (systolic or diastolic) should also be considered in interpreting plasma BNP concentrations in HF patients. These findings may contribute to the clinical management of HF patients, especially those complicated with CKD and ESRD.

Genetic Polymorphisms of the Natriuretic Peptide System in the Pathogenesis of Cardiovascular Disease: What Lies on the Horizon?

Background: The natriuretic peptide hormone family includes various proteins characterized by similar chemical structure and shared biological functions, with important effects on the cardiovascular system. Accordingly, these molecules are widely recognized as key clinical biomarkers in the diagnosis and monitoring of heart failure, hypertension, and coronary heart disease.

Content: Several single-nucleotide polymorphisms have been recently identified in genes associated with the natriuretic system. This review provides an overview of new insights into the functional role of these genetic variants, as well as their impact on cardiovascular physiopathology and drug response.

Conclusions: Noteworthy relationships between some specific polymorphisms and clinical correlates of cardiovascular disease have emerged. Nevertheless, future confirming studies are needed to substantiate the clinical relevance of such variants.

Cardiac markers: a clear cause for point-of-care testing

Point-of-care testing (POCT) in patients with ischemic heart disease is driven by the time-critical need for fast, specific, and accurate results to initiate therapy instantly. According to current guidelines, the results of the cardiac marker testing should be available to the physician within 30 min ("vein-to-brain" time) to initiate therapy within 60-90 min ("door-to-needle" time) after the patient has arrived at the emergency room or intensive care unit. This article reviews the current efforts to meet this goal (1) by implementing POCT of established biochemical markers such as cardiac troponins, creatine kinase MB, and myoglobin, in accelerated diagnosis and management workflow schemes, (2) by improving current POCT methods to obtain more accurate, more specific, and even faster tests through the integration of optical and electrochemical sensor technology, and (3) by identifying new markers for the very early and sensitive detection of myocardial ischemia and necrosis. Furthermore, the specific requirements for cardiac POCT in regard to analytical performance, comparability, and diagnostic sensitivity/specificity are discussed. For the future, the integration of new immunooptical and electrochemical chip technology might speed up diagnosis even further. However, every new development will have to meet the stringent method validation criteria set for corresponding central laboratory testing.

Introduction of an NT-proBNP assay to an acute admission unit--a 2-year audit

BACKGROUND

The differential diagnosis of dyspnoea is difficult due to the low predictive value of clinical and laboratory parameters. The elevated levels of NT-proBNP in congestive heart failure may improve diagnostic accuracy. We have evaluated the effect of the introduction of an NT-proBNP assay on hospital length of stay (LOS) and mortality.

METHODS

There were 11,853 AMAU patient episodes in the 22 months study period (March 2005-Dec 2006). An NT-proBNP assay was requested in 657 (5.5%) of these. Comparison between categorical variables such as diagnosis, NT-proBNP testing, LOS, and in-hospital mortality was made using Chi-square tests. Literature review suggested that an NT-proBNP cut-off >or=5000 ng/L should predict acute in-patient mortality. Logistic regression analysis was used to examine the association between such an elevated NT-proBNP level and outcomes.

RESULTS

Of the 396 patients with NT-proBNP <5000 ng/L, 8.1% died compared with 22.5% of the 178 patients dying with values >or=5000 ng/L (p<0.0001). An NT-proBNP >or=5000 ng/L was predictive of both LOS >or=9 days (odds ratios (OR) 1.54 (95% CI 1.06, 2.24: p=0.02) and LOS >or=14 days (OR=1.87 (95% CI 1.29, 2.71: p=0.0009). NT-proBNP requests increased over time, from 2.6% to 8.2% of all patients; the result fell in the diagnostic range for CHF in 60% of requests.

CONCLUSION

The introduction of an NT-proBNP was reflected in an appropriate but rapidly increasing pattern of requests from clinicians. High NT-proBNP levels predicted in-hospital mortality and longer LOS in an acute medical population.

Cardiovascular biomarkers: increasing impact of laboratory medicine in cardiology practice

The practice of cardiology is in continual evolution, in parallel with the progress achieved by medical research in understanding the pathophysiology of cardiovascular disease and in developing new therapeutic procedures. Consequently, manufacturers of cardiac biomarkers are pressed with new demands to improve the performance of the existing and the development of novel ones. Several highly sensitive and/or specific assays for myocardial ischemic damage and myocardial function detection have already become commercially available. Moreover, an increasing number of novel risk factors have been added to the classical risk factors of cardiovascular disease. Finally, the recent surge of genetic analysis procedures will likely soon provide the clinical cardiologist with a number of laboratory tests for defining the molecular diagnosis, assessing new risk factors, and better targeting the pharmaceutical approaches in patients with cardiovascular disease. In this review, we first present the general characteristics of a biomarker followed by the analytical and clinical performance of assay methods.

BNP or NTproBNP? A clinician's perspective

Existing literature on two natriuretic peptides--B-type natriuretic peptide (BNP) and amino terminal pro-brain natriuretic peptide (NTproBNP)--is overwhelming. Both peptides are acknowledged markers for cardiac dysfunction. Most of the sources present data on either BNP or NTproBNP making the comparison difficult. This paper focuses on reviewing studies directly comparing two peptides in the setting of chronic and acute heart failure (HF) and coronary artery disease. Many concomitant diseases influence these two peptides to varying extent. These characteristics should be taken into consideration when interpreting results. For most practical purposes, BNP and NTproBNP are interchangeable, and can be used based on local preferences and availability. NTproBNP seems to be more advantageous for diagnosing mild HF or asymptomatic left ventricular dysfunction.

NT-pro-BNP during hypoglycemia and hypoxemia in normal subjects: impact of renin-angiotensin system activity

Brain-derived natriuretic peptide (BNP) is a cardioprotective peptide released, together with the inactive NH(2)-terminal part of its prohormone (NT-pro-BNP), in response to different kinds of myocardial stress. Hypoglycemia and hypoxemia are conditions that threaten cellular function and hence potentially stimulate BNP release. BNP interacts with the renin-angiotensin system (RAS). The aim of this study was, therefore, to explore if basal RAS activity has an impact on NT-pro-BNP concentrations during myocardial stress induced by hypoglycemia and hypoxemia. From a cohort of 303 healthy young men, 10 subjects with high-RAS activity and 10 subjects with low-RAS activity (age 26 +/- 1 yr; mean +/- SE) were studied in a single-blinded, randomized, counterbalanced, crossover study on three occasions separated by at least 3 wk: 1) hypoglycemia (mean nadir plasma glucose 2.7 +/- 0.5 mmol/l), 2) hypoxemia (mean nadir Po(2) 5.8 +/- 0.5 kPa), and 3) normoglycemic normoxia (control). NT-pro-BNP was measured at baseline, during the stimuli, and in the recovery phase. Hypoxemia was associated with a 9% increase in NT-pro-BNP from 2.2 +/- 1.5 pmol/l at baseline to 2.4 +/- 1.5 pmol/l during hypoxemia (P < 0.001). Hypoglycemia did not affect the NT-pro-BNP level. RAS activity had no impact on NT-pro-BNP levels during hypoglycemia and hypoxemia. Hypoxemia, but not hypoglycemia, stimulates NT-pro-BNP. This indicates that cardiac defense mechanisms against hypoglycemia, if any, are probably different from those against hypoxemia. Basal RAS activity had no impact on NT-pro-BNP levels.

Clinical relevance of measurement of brain natriuretic peptide and N-terminal pro-brain natriuretic peptide in pediatric cardiology

BACKGROUND

The aim of this review is to understand the clinical usefulness of Brain Natriuretic Peptide (BNP) and N-terminal pro-Brain Natriuretic Peptide (NT-proBNP) in pediatric cardiology.

METHODS

A computerized literature search on National Library of Medicine using the keywords "BNP assay" and "NT-proBNP assay" was performed. Then, we refined the analysis to include only the studies specifically designed to evaluate the clinical usefulness of BNP and NT-proBNP assays in patients with congenital heart disease.

RESULTS

BNP and NT-proBNP are useful marker for diagnosis of heart failure, for the assessment of clinical severity and for the follow-up of congenital and pediatric heart diseases. However, results from different studies are often partial and not always univocal. Moreover, reference intervals in pediatric population have not yet been extensively evaluated.

CONCLUSIONS

BNP and NT-proBNP may be considered helpful markers for the integrated diagnosis and management of pediatric patients, though further studies are needed to support their routine use.

Influence of sample matrix and storage on BNP measurement on the Bayer Advia Centaur

The assessment and management of congestive heart failure relies increasingly on the measurement of B-type natriuretic peptide (BNP). However, the effective contribution of this biochemical test in the clinical decision making is influenced by reliability of the measure, which also depends on several preanalytical issues. Since there is controversy on the influence of the matrix and the storage conditions on BNP measurement, we compared results of BNP in serum, K2 ethylene diamine tetra-acetic acid (EDTA) plasma and lithium heparin plasma fresh samples and in matching samples stored at -20 and -80 degrees C for 1 week. BNP measured on the Bayer Advia Centaur was systematically underestimated in heparin plasma (-47%) and serum (-62%) when compared to K2 EDTA plasma. According to the established 100 ng/L cutoff value, 25% and 37% of the fresh samples collected in heparin plasma or serum were misclassified from the reference K2 EDTA fresh specimen, respectively. When compared to the fresh specimens, the mean and interindividual bias observed for samples stored at either -20 degrees C or -80 degrees C was, overall, modest for K2 EDTA plasma (-2%) and heparin plasma (+6% and -4%, respectively), though it appeared clinically meaningful in serum (+47% and +28%, respectively). Although we can not rule out that other BNP assays using different antibodies may be not affected from degradation during storage to the same extent, results of our investigation demonstrate that K2 EDTA plasma is the most suitable specimens for BNP testing on fresh and frozen samples stored at either -20 degrees C or -80 degrees C for up to 1 week.

Evidence for the use of B-type natriuretic peptides for screening asymptomatic populations and for diagnosis in primary care

OBJECTIVES

To determine the screening and diagnostic properties of BNP and NT-proBNP for heart failure in primary care.

DESIGN AND METHODS

We conducted a systematic review of randomized control trials and observational (cohort or case-control) studies of heart failure detection using B-type natriuretic peptides published in English from January 1989 to February 2005. We extracted or calculated sensitivity, specificity, positive and negative likelihood ratios, area under the receiver-operator characteristic curve and diagnostic odds ratio (DOR).

RESULTS

We included 17 studies (7 screening, 9 diagnosis in primary care or specialised clinic, 1 both). There was considerable heterogeneity within the study populations, reference standard for diagnosis, and B-type natriuretic peptide decision point. Sensitivity ranged from 26% to 98%; and specificity from 44% to 88%. For screening, the Diagnostic Odds Ratio (DOR) ranged from 2.7 to 29, and for diagnosis from 2.8 to 137.

CONCLUSIONS

The performance characteristics of B-type natriuretic peptides measurement are not suitable for screening asymptomatic patients. For diagnosis in primary care, low B-type natriuretic peptide values may be used to rule-out heart failure but, due to poor specificity, high values cannot be used to rule-in the condition.