Natriuretic peptides as markers of mild forms of left ventricular dysfunction: effects of assays on diagnostic performance of markers

Prognostic value of N-terminal Pro–B-Type natriuretic peptide in patients with intermediate coronary lesions

Background

The optimal treatment strategy for patients with coronary intermediate lesions, defined as diameter stenosis of 50–70%, remains a great challenge for cardiologists. Identification of potential biomarkers predictive of major adverse cardiovascular events (MACEs) risk may assist in risk stratification and clinical decision.

Methods

A total of 1,187 patients with intermediate coronary lesions and available N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were enrolled in the current study. A baseline NT-proBNP level was obtained. The primary endpoint was defined as MACEs, the composite endpoint of all-cause death and non-fatal myocardial infarction. A multivariate Cox regression model was used to explore the association between NT-proBNP level and MACE risk.

Results

The mean age of the study cohort was 59.2 years. A total of 68 patients experienced MACE during a median follow-up of 6.1 years. Restricted cubic spline analysis delineated a linear relationship between the baseline NT-proBNP level and MACE risk. Both univariate and multivariate analyses demonstrated that an increased NT-proBNP level was associated with an increased risk of MACE [adjusted hazard ratio (HR) per doubling: 1.412, 95% confidence interval (CI): 1.022–1.952, p = 0.0365]. This association remains consistent in clinical meaningful subgroups according to age, sex, body mass index (BMI), and diabetes.

Conclusion

An increased NT-proBNP level is associated with an increased risk of MACE in patients with intermediate coronary lesions and may serve as the potential biomarker for risk stratification and treatment decision guidance.

Urinary N-terminal pro-brain natriuretic peptide: prognostic value in patients with acute chest pain

AIMS

The objective of this study was to investigate the prognostic value of urinary N-terminal pro-brain natriuretic peptide (NT-proBNP) compared with plasma NT-proBNP in patients presenting with acute chest pain in the emergency department.

METHODS AND RESULTS

We measured simultaneously plasma and urinary NT-proBNP at admission in 301 patients with acute chest pain. In our cohort, 174 patients suffered from acute coronary syndrome (ACS). A follow-up (median of 55 months) was performed regarding the endpoints all-cause mortality and major adverse cardiac events (mortality, congestive heart failure, ACS with the necessity of a coronary intervention, and stroke). Fifty-four patients died during follow-up; 98 suffered from the combined endpoint. A significant and positive correlation of urinary and plasma NT-proBNP was found (r = 0.87, P < 0.05). Patients with troponin positive ACS had significantly elevated levels of plasma and urinary NT-proBNP compared with those with unstable angina pectoris or chest wall syndrome (each P < 0.05). The highest levels of both biomarkers were found in patients with congestive heart failure (each P < 0.05). According to Kaplan-Meier analysis, plasma and urinary NT-proBNP were significant predictors for mortality and the combined endpoint in the whole study cohort and in the subgroup of patients with ACS (each P < 0.05). Regarding Cox regression analysis, plasma and urinary NT-proBNP were independent predictors for mortality and the combined endpoint (each P < 0.05).

CONCLUSIONS

Urinary NT-proBNP seems to provide a significant predictive value regarding the endpoints all-cause mortality and major adverse cardiac events in patients with acute chest pain and those with ACS.

Prognostic Role of B-Type Natriuretic Peptide in Adults with Acute Dyspnea Requiring Emergency Admission

Objective:

The aim of the study was to evaluate the role of B-type natriuretic peptide (BNP) in patients presenting with acute dyspnea admitted in emergency services.

Materials and Methods:

A prospective observational study was conducted on 100 patients presenting to the emergency of Dayanand Medical College and Hospital and Hero DMC Heart Institute with acute dyspnea of <48 h duration, in which BNP levels were done on arrival to emergency.

Results:

BNP levels were significantly higher in patients having left ventricular dysfunction, both systolic and diastolic. Patients with systolic dysfunction had slightly higher BNP (1251.50 ±950.14 pg/mL) compared to patients with diastolic dysfunction (905.62±618.10 pg/mL) though statistically insignificant (P = 0.055). BNP levels were also inversely related to ejection fraction. Mean BNP levels in patients with EF <31%, 31%–45%, 46%–59%, and ≥60% were 1464.63 ± 1058.29, 968.24 ± 751.59, 841.64 ± 503.41 and 781.67 ± 504.21 (P = 0.009), respectively. Patients having higher BNP levels had significantly prolonged duration of stay compared to patients with lower BNP. Patients who expired had slightly higher levels of BNP though statistically nonsignificant. BNP had no significant statistical relation with age, heart rate, creatine phosphokinase-MB, Trop-T levels, systolic blood pressure.

Conclusion:

We conclude that high BNP levels are a marker of cardiac dysfunction and increased duration of hospital stay in patients presenting to the emergency with acute dyspnea. Hence, BNP can be used as a screening test for the evaluation and management of dyspnea.

B-Type Natriuretic Peptide as a Significant Brain Biomarker for Stroke Triaging Using a Bedside Point-of-Care Monitoring Biosensor

Stroke is a widespread condition that causes 7 million deaths globally. Survivors suffer from a range of disabilities that affect their everyday life. It is a complex condition and there is a need to monitor the different signals that are associated with it. Stroke patients need to be rapidly diagnosed in the emergency department in order to allow the admission of the time-limited treatment of tissue plasminogen activator (tPA). Stroke diagnostics show the use of sophisticated technologies; however, they still contain limitations. The hidden information and technological advancements behind the utilization of biomarkers for stroke triaging are significant. Stroke biomarkers can revolutionize the way stroke patients are diagnosed, monitored, and how they recover. Different biomarkers indicate different cascades and exhibit unique expression patterns which are connected to certain pathologies in the human body. Over the past decades, B-type natriuretic peptide (BNP) and its derivative N-terminal fragment (NT-proBNP) have been increasingly investigated and highlighted as significant cardiovascular biomarkers. This work reviews the recent studies that have reported on the usefulness of BNP and NT-proBNP for stroke triaging. Their classification association is also presented, with increased mortality in stroke, correlation with cardioembolic stroke, and an indication of a second stroke recurrence. Moreover, recent scientific efforts conducted for the technological advancement of a bedside point-of-care (POC) device for BNP and NT-proBNP measurements are discussed. The conclusions presented in this review may hopefully assist in the major efforts that are currently being conducted in order to improve the care of stroke patients.

Detection of B-type natriuretic peptide by establishing a low-cost and replicable fluorescence resonance energy transfer platform

Aiming at the establishment of a sensitive and specific diagnostic method for early heart failure (HF), we developed a cost-effective fluorescence resonance energy transfer (FRET) platform for the detection of B-type natriuretic peptide (BNP), a characteristic biomarker of HF. Graphene oxide (GO) was selected as the FRET receptor in view of its advantages including commercial availability, low-cost and chemical stability, and dye-modified aptamer was used as the energy donor of FRET as well as in charge of the specific recognition of BNP. Based on the ON (strong emission) and OFF (quenching) states of FRET in the presence and absence of BNP, respectively, specific detection of BNP was achieved in the range 0.074-0.56 pg/mL with a limit of detection as low as 45 fg/mL (3σ). This FRET platform was applied to detect BNP in 45 blood samples to demonstrate its practicability in clinical diagnosis. Compared to the commonly used Siemens method (chemiluminescence immunoassay, CLIA) in hospital, our approach is more accurate and specific for HF diagnosis with areas under the receiver operating characteristic curves of 0.869 (95% CI 0.733-1.00, P < 0.05) vs 0.850 (95% CI 0.703-0.997, P < 0.05) and specificity of 68.8% vs 65.6%. This platform is promising in early diagnosis of HF through ultrasensitive and specific detection of BNP. Graphical abstract To solve the clinical diagnostic problem for early heart failure (HF) which lacks sensitivity and specificity, we established a cost-effective and rapid fluorescence analysis method based on fluorescence resonance energy transfer (FRET) platform for the detection of B-type natriuretic peptide (BNP), a characteristic biomarker of HF.

SOMAscan-based proteomic measurements of plasma brain natriuretic peptide are decreased in mild cognitive impairment and in Alzheimer's dementia patients

Alzheimer's disease represents the most common age-related neurodegenerative disorder and a leading cause of progressive cognitive impairment. Predicting cognitive decline is challenging but would be invaluable in an increasingly aging population which also experiences a rising cardiovascular risk. In order to examine whether plasma measurements of one of the established biomarkers of heart failure, brain natriuretic peptide (BNP), reflect a decline in cognitive function, associated with Alzheimer's disease neurodegeneration, BNP levels were analysed, by using a novel assay called a SOMAscan, in 1. cognitively healthy, control subjects; 2. subjects with mild cognitive impairment, and 3. subjects with Alzheimer's disease. The results of our study show that the levels of the BNP were significantly different between the three types of diagnoses (p < 0.05), whereby subjects with mild cognitive impairment had the lowest mean BNP value, and healthy subjects had the highest BNP value. Importantly, our results show that the levels of the BNP are influenced by the presence of at least one APOE4 allele in the healthy (p < 0.05) and in the Alzheimer's disease groups of subjects (p < 0.1). As the levels of the BNP appear to be independent of the APOE4 genotype in subjects with mild cognitive impairment, the results of our study support inclusion of measurements of plasma levels of the BNP in the list of the core Alzheimer's disease biomarkers for identification of the mild cognitive impairment group of patients. In addition, the results of our study warrant further investigations into molecular links between Alzheimer's disease-type cognitive decline and cardiovascular disorders.

Establishment of normal reference values of NT-proBNP and its application in diagnosing acute heart failure in children with severe hand foot and mouth disease [corrected]

Hand, foot, and mouth disease (HFMD), caused by enteroviruses, is an acute contagious disease in children. Some severe infections caused by human enterovirus 71 (HEV71) lead to rapid death in children with acute heart failure (HF). N-terminal probrain natriuretic peptide (NT-proBNP) is an important indicator of HF; however, its normal reference values in children and role in HFMD remain unclear.This study aimed to investigate the correlation between NT-proBNP and heart function and establish normal reference values of NT-proBNP in children with HFMD aged 0 to 18 years.In this study, 95% normal reference values were established in 1031 healthy children aged 0 to 18 years. The correlation between NT-proBNP and left ventricular ejection (LVEF) was analyzed in 392 children with HFMD using Spearman correlation and receiver operating characteristic analysis.NT-proBNP levels were negatively correlated with LVEF in 392 children with HFMD. The median NT-proBNP level was 921 pg/mL in the early cardiorespiratory failure group, but only 55 pg/mL in the nervous system involvement group. Serum NT-proBNP levels were negatively correlated with age. The normal reference value in the neonatal period (0 to <1 month) and adolescence (13-18 years) was 250.0 to 3987.0 pg/mL and 20.0 to 145.0 pg/mL, respectively.NT-proBNP levels can reflect the severity of HFMD and discriminate the second stage from the third stage of HFMD effectively. NT-proBNP is a useful biomarker to predict the early stage of severe HFMD in children with HF. Different ages fit with different normal reference values of NT-proBNP in children.

Natriuretic peptides in the control of lipid metabolism and insulin sensitivity

Natriuretic peptides have long been known for their cardiovascular function. However, a growing body of evidence emphasizes the role of natriuretic peptides in human substrate and energy metabolism, thereby connecting the heart with several insulin-sensitive organs like adipose tissue, skeletal muscle and liver. Obesity may be associated with an impaired regulation of the natriuretic peptide system, also indicated as a natriuretic handicap. Evidence points towards a contribution of this natriuretic handicap to the development of obesity, type 2 diabetes mellitus and cardiometabolic complications, although the causal relationship is not fully understood. Nevertheless, targeting the natriuretic peptide pathway may improve metabolic health in obesity and type 2 diabetes mellitus. This review will focus on current literature regarding the metabolic roles of natriuretic peptides with emphasis on lipid metabolism and insulin sensitivity. Furthermore, it will be discussed how exercise and lifestyle intervention may modulate the natriuretic peptide-related metabolic effects.

Atrial natriuretic peptide and type 2 diabetes development--biomarker and genotype association study

BACKGROUND

We have recently shown that low plasma levels of mid-regional atrial natriuretic peptide (MR-ANP) predict development of diabetes and glucose progression over time, independently of known risk factors for diabetes development. However, since MR-ANP levels might be influenced by unknown factors causing diabetes, we cannot rule out that such relationship might be confounded. Previous studies have shown an association of a single nucleotide polymorphism rs5068 on the natriuretic peptide precursor A (NPPA) locus gene with higher levels of circulating ANP. Since gene variants are inherited randomly and not subject to confounding, we aimed to investigate whether the variant rs5068 within the NPPA locus is associated with incident type 2 diabetes.

METHODS

We genotyped the variant rs5068 within the NPPA locus in 27,307 individuals without known diabetes from the Malmö Diet Cancer Study. Incident diabetes was retrieved through national and regional registers (median follow-up time of 14 years, 2,823 incident diabetes cases).

RESULTS

In Cox regression analysis adjusted for age, sex and BMI, we found that the carriers of at least one copy of the G allele of rs5068 had lower likelihood of incident diabetes within 14 years (HR = 0.88, 95% CI 0.78-0.99, p = 0.037).

CONCLUSION

Our results indicate a role of the ANP system in the etiology of type 2 diabetes and might help provide insight in the metabolic actions of natriuretic peptides and the pathophysiology of type 2 diabetes.

N-terminal proBNP: a novel biomarker for the diagnosis, risk stratification and management of congestive heart failure

Congestive heart failure is a leading cause of morbidity and mortality throughout the world and is now the leading cause of hospitalizations in adults over 65 years of age with an estimated annual expenditure in excess of USD 20 billion. In addition, it is the only cardiovascular disorder that continues to increase in both incidence and prevalence, and as the population continues to age, it is expected that the prevalence of this disease will continue to rise. Ironically, the armamentarium of medications that decrease mortality due to congestive heart failure also continues to grow; however, the relative number of eligible patients with congestive heart failure (or at risk for congestive heart failure) that receive these important therapies remains low. Thus, better tools to aid the early diagnosis and management of this disease are needed. Testing for natriuretic peptide markers, such as B-type natriuretic peptide or its amino-terminal fragment, has emerged as an important tool to assist in the optimal diagnosis and risk stratification of patients with congestive heart failure and may also play a valuable role in guiding therapy.

Amino-terminal pro-brain natriuretic peptide: a biomarker for diagnosis, prognosis and management of heart failure

There is a substantial need for a diagnostic tool to aid in the early diagnosis of heart failure and in the recognition of those at risk for its development, as well as in guidance of therapy. Testing for amino-terminal pro-brain natriuretic peptide (NT-proBNP) has been recognized to have utility in the diagnosis, prognosis and management of heart failure. In addition, numerous other applications for NT-proBNP testing are now recognized, such as evaluation of patients with heart disease in the absence of heart failure, as well as the diagnostic and prognostic evaluation of patients with acute coronary syndromes or pulmonary thromboembolism.

The diagnostic utility of brain natriuretic peptide in heart failure patients presenting with acute dyspnea: a meta-analysis

Heart failure with normal ejection fraction (HFNEF) accounts for approximately 50% of heart failure (HF) cases. To establish the utility of brain natriuretic peptide (BNP) in differentiating HF-related severe dyspnea from non-HF-related acute dyspnea, we used an estimation formula (eF) that was obtained from a series of three meta-regressions. We selected 60 out of 2721 case-control and follow-up studies that were published from 1998 to 2010. The heart failure levels (HFLs) were assessed using the New York Heart Association (NYHA) criteria. Random-effects meta-regression analyses of the natural logarithm (ln) of the BNP odds ratio (OR) were performed on the HFLs. The ln of the median BNP values (lnmBNP) was meta-regressed over the laboratory method (LM). A third meta-regression was performed on the HFLs to account for only the lnmBNP in the homogeneous LM subgroups. To determine the eF, the data from the diseased and control subjects were combined. The Bland-Altman method was used to detect eF bias. The overall BNP(OR) in the subgroup with severe HF was 35. The lnmBNP analysis showed that LM was a significant heterogeneity factor in the meta-regression (slope −0.38; CI −0.59 to −0.16). The meta-regression of lnmBNP on the HFL resulted in the following calculation for eF: estimated HFL (eHFL)=(lnmBNP–3.157)/0.886. The Bland-Altman test revealed no significant difference (0.0997; 95% CI −2.84 to 3.06) between HFL and eHFL. The severe eHFL showed a 78% accuracy. Based on the eF obtained from this meta-analysis, the BNP outcomes were shown to reliably diagnose severe dyspnea in HF and differentiate this condition from non-HF acute dyspnea.

Equal performance of novel N-terminal proBNP (Cardiac proBNP®) and established BNP (Triage BNP®) point-of-care tests

Background: Recently, a novel point-of-care test (POCT) for N-terminal proBNP (NTproBNP) has been introduced (Cardiac proBNP®, Roche). Aim: The aim was to compare the novel POCT for NTproBNP with the established POCT for BNP. Methods: NTproBNP and BNP were assessed in 222 individuals with chronic heart failure (n = 151) or controls (n = 71) with both POCTs. Results: NTproBNP and BNP were closely correlated upon regression analysis (r = 0.93; p < 0.01). NTproBNP and BNP were both correlated with ejection fraction and New York Heart Association stage. Receiver operating characteristic analysis yielded satisfying and equivalent predictive values for the detection of left ventricular dysfunction (ejection fraction <40%; NTproBNP: area under the curve 0.97; BNP: area under the curve 0.96; p > 0.05) and presence of New York Heart Association stage >2 (area under the curve 0.92 vs 0.91 for NT-proBNP and BNP, respectively; p > 0.05). Conclusion: The NTproBNP POCT allows biochemical detection of heart failure with satisfactory predictive values, is equivalent to the BNP POCT and will improve near-patient testing.

Serum 25-hydroxyvitamin D and parathyroid hormone in relation to plasma B-type natriuretic peptide: the Hoorn Study

OBJECTIVE

A disturbed vitamin D-parathyroid hormone (PTH)-calcium axis may play a role in the pathogenesis of heart failure. Therefore, we investigated whether lower 25-hydroxyvitamin D (25(OH)D) and higher PTH are cross sectionally and after 8 years of follow-up associated with higher B-type natriuretic peptide (BNP) levels in older men and women.

DESIGN AND METHODS

We measured baseline 25(OH)D, PTH, and BNP in 502 subjects in 2000-2001 in the Hoorn Study, a population-based cohort. Follow-up BNP was available in 2007-2009 in 278 subjects. Subjects were categorized according to season- and sex-specific quartiles of 25(OH)D and PTH at baseline. We studied the association of 25(OH)D and PTH quartiles with BNP using linear regression analyses adjusting for confounders. Analyses were stratified by kidney function estimated glomerular filtration rate (eGFR; ≤60 ml/min per 1.73 m(2)) because of significant interaction.

RESULTS

At baseline, subjects had a mean age of 69.9±6.6 years, mean 25(OH)D level was 52.2±19.5 nmol/l and mean PTH 6.1±2.4 pmol/l. Cross sectionally, 25(OH)D was associated with BNP in subjects with impaired kidney function (eGFR ≤60 ml/min) only. The association attenuated after adjustment for PTH. PTH was cross sectionally associated with BNP, also in subjects with impaired kidney function only: regression coefficient of highest quartile 9.9 pmol/l (95% confidence interval 2.5, 17.4) with a significant trend across quartiles. Neither 25(OH)D nor PTH was associated with BNP in longitudinal analyses.

CONCLUSION

This study showed overall no strong association between 25(OH)D and BNP. However, PTH was associated with BNP in subjects with impaired kidney function and may point to a potential role in myocardial function.

Low plasma level of atrial natriuretic peptide predicts development of diabetes: the prospective Malmo Diet and Cancer study

CONTEXT

The cardiac natriuretic peptides are involved in blood pressure regulation, and large cross-sectional studies have shown lower plasma levels of N-terminal pro-natriuretic peptide levels [N-terminal atrial natriuretic peptide (N-ANP) and N-terminal brain natriuretic peptide (N-BNP)] in patients with insulin resistance, obesity, and diabetes.

OBJECTIVE

In this study, we prospectively tested whether plasma levels of mid-regional ANP (MR-ANP) and N-BNP predict new-onset diabetes and long-term glucose progression.

DESIGN, SETTING, AND PATIENTS

MR-ANP and N-BNP were measured in 1828 nondiabetic individuals of the Malmö Diet and Cancer cohort (mean age 60 yr; 61% women) who subsequently underwent a follow-up exam including an oral glucose tolerance test after a median follow-up time of 16 yr. Logistic regression was used to adjust for covariates.

RESULTS

During follow-up, 301 subjects developed new-onset diabetes. After full multivariate adjustment, MR-ANP was significantly inversely associated with incident diabetes (OR = 0.85; 95% CI = 0.73-0.99; P = 0.034) but not N-BNP (OR = 0.92; 95% CI = 0.80-1.06; P = 0.262). In fully adjusted linear regression models, the progression of fasting glucose during follow-up was significantly inversely related to baseline levels of MR-ANP (P = 0.004) but not N-BNP (P = 0.129). Quartile analyses revealed that the overall association was mainly accounted for by excess risk of incident diabetes in subjects belonging to the lowest quartile of MR-ANP. After full adjustment, the odds ratio for incident diabetes in the bottom compared with the top quartile of MR-ANP was 1.65 (OR = 1.08-2.51, P = 0.019) and 1.43 (OR = 1.04-1.96, P = 0.027) compared with all other subjects.

CONCLUSION

Low plasma levels of MR-ANP predict development of future diabetes and glucose progression over time, suggesting a causal role of ANP deficiency in diabetes development.

Assessment of cardiac involvement of hepatitis C virus; tissue Doppler imaging and NTproBNP study

INTRODUCTION

Hepatitis C disease burden is substantially increasing in Egyptian community, it is estimated that prevalence of Hepatitis C virus (HCV) in Egyptian community reach 22% of total population. Recently there is a global alert of HCV cardiovascular complications.

OBJECTIVE

To evaluate LV diastolic functions of HCV patients using tissue Doppler Imaging and NTPBNP.

METHODS

30 HCV patients of 30 years, sex & BMI matched controls were evaluated by PCR, ECG, Echocardiography "conventional Doppler, pulsed wave tissue Doppler (PW-TD), strain rate imaging" & NTPBNP to assess LV diastolic functions. Mean age was 32.8 years ± 5.1 in HCV group, 29.8 years ± 6.6 in control group. Cardiovascular anomalies and predisposing factors were excluded.

RESULTS

HCV group has shown significant increase in QTc interval, significant statistical increase in A wave, deceleration time; (p < 0.05), highly significant decrease in tissue Doppler E a (p < 0.001), highly significant decrease in A a (p < 0.001), highly significant increased E/E a ratio (p value < 0.001), significant decrease in E a/A a ratio and significant increase in SRa (p < 0.05). NTPBNP levels showed highly significant increase with mean value 222 pg/ml ± 283 in HCV group and 32.7 pg/ml ± 21.2 in control group (p value < 0.001). The best cut-off value of NTPBNP to detect diastolic dysfunction in HCV group was 213 pg/ml. No statistical differences in SRe/SRa and E/SRe ratios were observed, however they had significant correlation with NTPBNP level and tissue Doppler parameters. The best cut-off value of E/SRe ratio to detect diastolic dysfunction in HCV group was 0.91, with 75% sensitivity and 100% specificity.

CONCLUSION AND RECOMMENDATION

This data show the first direct evidence that HCV infection causes diastolic dysfunction without any other predisposing factors, probably due to chronic inflammatory reaction with mild fibrosis in the heart. Previous studies did not follow strict inclusion and exclusion criteria that confirm the independent role of HCV to cause diastolic dysfunction. Tissue Doppler was more sensitive to diagnose diastolic dysfunction than conventional Doppler.

Characterization of Molecular Forms of N-Terminal B-Type Natriuretic Peptide In Vitro

BACKGROUND

The heterogeneity of circulating peptides may influence the interpretation of results from N-terminal profragment of BNP (NT-proBNP) assays. Our objective was to characterize the heterogeneity for better usability of the assays.

METHODS

Endogenous proBNP was purified from patient samples and treated with trifluoromethanesulfonic acid (chemical deglycosylation). The human proBNP gene was introduced into rat hearts by adenoviral transfer. Cell lysates and plasma samples containing proBNP-derived peptides were analyzed by chromatography. The fate of exogenous recombinant NT-proBNP added to fresh whole blood samples was followed by immunoassays and chromatography. The main NT-proBNP components were isolated and identified by mass spectrometry.

RESULTS

Immunoreactive NT-proBNP in human plasma comprised several molecular forms, as did circulating immunoreactive human NT-proBNP after adenoviral transfer of human proBNP cDNA into rat ventricular myocardium. Incubation of recombinant NT-proBNP1–76 in human plasma or serum resulted in multiple components with the 2 major components identified as NT-proBNP1–36 and NT-proBNP1–62/64. Profiling by different antisera and chromatography indicated masking of the non–mid-region epitopes likely due to formation of oligomers. More than 75% of the original immunoreactivity in the mid-region epitope was retained after 3-week storage of plasma samples at room temperature.

CONCLUSIONS

There is marked heterogeneity in immunoreactive NT-proBNP in plasma not related to glycosylation. The mid-region epitope of NT-proBNP is stable even in harsh storage conditions. Careful choice of antibody epitopes can yield extraordinarily robust assays.

Strong relationship between NT-proXNP levels and cardiac output following cardiac surgery in neonates and infants

BACKGROUND

NT-proXNP, a new natriuretic peptide analyte, incorporates information about the concentrations of both N-terminal pro-atrial and pro-brain natriuretic peptides (NT-proANP, NT-proBNP). We aimed to investigate whether NT-proXNP is a reliable indicator of the cardiac index (CI) and the hemodynamic state in neonates and infants undergoing an open heart surgery.

METHODS

We enrolled 26 children under the age of 1 year into this prospective study. All patients underwent an elective cardiac operation with cardiopulmonary bypass (CPB) to achieve complete biventricular repair. Peri-operative hemodynamic parameters were assessed by transpulmonary thermodilution and natriuretic peptide levels were recorded.

RESULTS

The NT-proXNP level correlated significantly with the simultaneously measured NT-proANP level (r=0.60, P<0.001), but more strongly with the NT-proBNP level (r=0.89, P<0.001) and the arithmetic sum of both (r=0.88, P<0.001). NT-proXNP had a strong correlation with CI (r=-0.85, P<0.001), the stroke volume index (r=-0.80, P<0.001) and the global ejection fraction (r=-0.67, P<0.009) throughout the post-operative period. Conventionally measured parameters such as heart rate, mean arterial pressure and pulse-pressure product exhibited weaker correlations with CI than NT-proXNP. Among laboratory values, creatinine levels correlated significantly with CI (r=-0.77, P<0.001) and NT-proXNP (r=0.76, P<0.001) during the post-operative period. A post-operative NT-proXNP level of 3079 pmol/l was diagnostic for CI <3 l/min/m(2) with 89% sensitivity and 90% specificity (area under the curve: 0.91 +/- 0.05).

CONCLUSION

NT-proXNP is a good marker of cardiac output following pediatric cardiac surgery and might be a useful tool in the recognition of a low output state.

Improvement of the cardiac marker N-terminal-pro brain natriuretic peptide through adjustment for renal function: a stratified multicenter trial

BACKGROUND

N-terminal-pro brain natriuretic peptide (NT-proBNP) is a useful cardiac marker that is also influenced by renal dysfunction. It was our objective to assess the relationship between NT-proBNP concentrations in plasma and worsening renal function, and to attempt adjustment of NT-proBNP for renal dysfunction in a prospective, stratified multi-center study.

METHODS

We stratified 203 male patients according to their cardiac status and the estimated glomerular filtration rate (eGFR). Cardiac disease was assessed by medical history, physical examination and standardized echocardiography. Patients were stratified according to the following: absence of cardiac history and abnormalities (control, CTRL, n=66), cardiac history without left ventricular hypertrophy (LVH) or left ventricular systolic dysfunction (LVD) (history, n=30), LVH without systolic dysfunction (LVH, n=68), and LVD [ejection fraction (EF) <40%, LVD, n=39]. Renal disease was stratified according to the eGFR: 15-30 mL/min (n=52), 31-75 mL/min (n=99), and >75 mL/min (n=52).

RESULTS

NT-proBNP was correlated with eGFR in the entire study population and for all levels of cardiac disease (all p<0.01). Regression analysis allowed adjustment of NT-proBNP for eGFR in a continuous manner, and this adjustment significantly improved the predictive value (receiver operating characteristic curve for symptomatic LVD from 0.80 to 0.86, p<0.01; sensitivity from 74% to 83% and specificity from 68% to 79%).

CONCLUSIONS

NT-proBNP correlates inversely and significantly with eGFR throughout all levels of cardiac strata. We propose for the first time a continuous adjustment algorithm which markedly improves the predictive values of NT-proBNP in male patients with impaired renal function.

N-terminal pro-brain natriuretic peptide from fresh urine for the biochemical detection of heart failure and left ventricular dysfunction

AIMS

Plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) is a strong biochemical marker of heart failure and left ventricular dysfunction (LVD). Due to renal arterio-venous clearance of NT-proBNP and the correlation of plasma concentrations with renal function, we hypothesized that NT-proBNP may have potential as a urinary marker. The objective of this study was to assess urinary concentrations of NT-proBNP and to identify the predictive value of urinary NT-proBNP for detecting LVD and heart failure.

METHODS AND RESULTS

N-terminal pro-brain natriuretic peptide (Elecsys proBNP((R)), Roche) was assessed simultaneously in fresh spot urine and plasma from 191 individuals. In patients with heart failure (n = 149), urinary and plasma NT-proBNP concentrations were positively correlated (r = 0.79, P < 0.001), but urinary NT-proBNP was significantly lower than plasma NT-proBNP (42 +/- 25 vs. 1389 +/- 325 pg/mL, P < 0.001). Upon receiver operating curve analysis, urinary NT-proBNP detected LV dysfunction (ejection fraction <40%) with a sensitivity of 91% and a specificity of 98% at a cutpoint of 22 pg/mL [area under the curves (AUC) 0.98]. At the same cutpoint, symptomatic heart failure (NYHA-class > 2) was detected with a sensitivity of 97% and specificity of 98% (AUC 0.99) and clinical signs of fluid retention were detected with a sensitivity and specificity of 98% each (AUC 0.99).

CONCLUSION

N-terminal pro-brain natriuretic peptide concentrations were markedly lower in the urine than in the plasma. However, urinary NT-proBNP levels increased stepwise with the severity of heart failure and LVD, and therefore yielded satisfactory predictive values for the detection of significant LVD and symptomatic heart failure. Measurement of urinary NT-proBNP is a novel, promising, and simple method for the biochemical detection of heart failure.

Simultaneous estimation of NT-proBNP on top to mitral flow Doppler echocardiography as an accurate strategy to diagnose diastolic dysfunction in HFNEF

BACKGROUND

Conventional echocardiography has limited accuracy in detecting diastolic dysfunction and NT-proBNP is known to be a reliable biomarker to rule out heart failure. Therefore NT-proBNP on top to conventional mitral flow Doppler might improve the diagnostic of diastolic dysfunction in patients with heart failure despite normal EF (HFNEF) without using tissue Doppler.

METHODS AND RESULTS

Diastolic function of 46 patients with HFNEF was determined by pressure-volume loop obtained by conductance-catheter measurements. LV stiffness correlated with the amount of collagen types I and III analyzed from endomyocardial biopsies (EMBs). NT-proBNP plasma levels correlated with LV stiffness, LVEDP and the collagen amount from EMBs (p<0.01). In another set of patients with HFNEF (n=107, 53 [45-62] years), diastolic dysfunction was confirmed by left and/or right heart catheterization. Their Doppler indices and plasma marker NT-proBNP values were compared with those of 73 controls (186 [70-342] vs 54[30-75] pg/ml, p<0.001). Mitral flow Doppler was impaired in 70/107 (65%) of the HFNEF. When additional criterium NT-proBNP>125 pg/ml was used 96/107 (90%) patients with impaired diastolic function were recognized. Sensitivity of tissue Doppler indices E'/A' and E/E' were improved by 4-6% using NT-proBNP on top. NT-proBNP recognized HFNEF patients with higher hospitalization rate indicated by phone questionnaire, whereas Doppler indices alone did not.

CONCLUSION

Plasma NT-proBNP levels are associated with increased LV stiffness and cardiac collagen content. On top measurements of plasma NT-proBNP improve the echocardiography diagnostic of diastolic function and prognostic of rehospitalization in HFNEF.

N-terminal pro-B-type natriuretic peptide and inducible ischemia in the Heart and Soul Study

BACKGROUND

B-type natriuretic peptide (BNP) is predictive of inducible ischemia in patients with coronary heart disease (CHD). Whether N-terminal pro-B-type natriuretic peptide (NT-proBNP) has a comparable strength of association with ischemia is uncertain.

HYPOTHESIS

Resting NT-proBNP levels are associated with inducible ischemia in patients with stable CHD.

METHODS

We performed a cross-sectional study of 901 outpatients with stable CHD. NT-proBNP was measured in all patients prior to exercise treadmill testing and stress echocardiography. In addition, plasma BNP was measured in a subset of 355 participants. Logistic regression was used to examine the association of NT-proBNP and BNP quartiles with inducible ischemia.

RESULTS

Inducible ischemia was found in 216 (24%) patients. The proportion with inducible ischemia ranged from 42% (95/225) in the highest quartile of NT-proBNP levels (>410 pg/ml) to 9% (21/226) in the lowest quartile (0-72 pg/ml). The highest quartile had a 7-fold greater odds of inducible ischemia than the lowest quartile (odds ratio [OR]: 7.1, 95% confidence interval [CI]: 4.2-12; P < 0.0001). This association remained robust after adjustment for traditional cardiovascular risk factors, left ventricular ejection fraction, and diastolic dysfunction (OR: 3.6, 95% CI: 1.4-9.1; P = 0.009). In the subgroup with measurements of both NT-proBNP and BNP, both natriuretic peptides were predictive of ischemia. The multivariable-adjusted c-statistics for inducible ischemia were 0.71 for NT-proBNP and 0.62 for BNP (entered as continuous variables).

CONCLUSIONS

Resting NT-proBNP levels are independently associated with inducible ischemia in outpatients with stable CHD. Baseline elevations of natriuretic peptide may indicate subclinical inducible ischemia in high risk patients with CHD.

Pediatric brain natriuretic peptide concentrations vary with age and sex and appear to be modulated by testosterone

BACKGROUND

Natriuretic peptide concentrations in adults require age- and sex-specific reference intervals for optimal interpretation. Females have higher natriuretic peptide concentrations, and hypotheses suggest that estrogen may be responsible. This study sought to determine the influence of hormone modulation on N-terminal probrain natriuretic peptide (NT-proBNP) by using a pediatric cohort. Children/adolescents typically have rapid hormone changes during puberty, making them an ideal group to study.

METHODS

We selected 759 specimens (303 male, 456 female; ages 2 months to 18 years, mean 13 years) obtained from the Mayo Clinic Pediatric Residual Specimen Bank. We measured NT-proBNP, sex hormone-binding globulin (SHBG), estradiol, and testosterone by immunoassays or LC-MS/MS and calculated free testosterone. We performed univariate and multivariate analyses to investigate the significance of NT-proBNP with each hormone.

RESULTS

Reference values demonstrated a sex difference and sequential age differences in females. Univariate modeling of the hormones with NT-proBNP revealed an independent inverse association of NT-proBNP with testosterone, a direct association with SHBG, and no significant association with estradiol. Multivariate modeling confirmed a strong association of testosterone and SHBG with NT-proBNP. Correlation of hormones with NT-proBNP retained greater significance than either age or sex.

CONCLUSIONS

In pediatric patients, NT-proBNP is independently associated with both testosterone and SHBG hormone concentrations. Measurements of testosterone are inversely associated with NT-proBNP, and estrogens are marginally associated with NT-proBNP in males but not females, suggesting that androgens and not estrogens modulate sex differences notable in natriuretic peptides. Children and adolescents may require an objective assessment of hormones if optimal interpretation of natriuretic peptide concentrations is desired or the concentrations are confounded. .

Diagnostic accuracy of plasma brain natriuretic peptide and aminoterminal‐proBNP in mild heart failure depends on assay and introduction of therapy

OBJECTIVE

A reliable biochemical marker of left ventricular dysfunction (LVD) could improve diagnostic accuracy. The aim of this study was to compare the correlation of measurements of brain natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) with different assays. The diagnostic accuracy of the tests in mild heart failure (HF) was estimated before and after the start of therapy.

MATERIAL AND METHODS

Doppler echocardiography and measurements of plasma BNP and NT-proBNP were performed in 150 patients.

RESULTS

Systolic dysfunction (LV ejection fraction 0.45) was present in 22 patients, and 58 had only abnormalities in LV filling. P-NT-proBNP based on two different assays demonstrated a moderate correlation (r = 0.57, p<0.0001) and a concentration-dependent systematic difference. Excellent correlation (r = 0.95, p<0.0001) was found between BNP and NT-proBNP based on two-site antibody assays, but was moderate between BNP and a one-site antibody NT-proBNP assay (r = 0.58, p<0.0001). Areas under the receiver operating characteristic (ROC) curves (AUCs) were 0.93 (95 % CI, 0.90-0.98) for BNP, 0.95 (0.91-0.99) for NT-proBNP (two-site antibody assay) and 0.77 (0.70-0.85) for the one-site antibody NT-proBNP assay (p = 0.0001). At re-evaluation of LVD at 6 and 12 months, AUCs of BNP were 0.81 (0.74-0.99) and 0.83 (0.76-0.89), respectively, and AUCs of NT-proBNP (two-site) were 0.84 (0.77-0.91) and 0.87 (0.81-0.93), respectively. Using the baseline threshold reduced the sensitivity and specificity of BNP and NT-proBNP measurements.

CONCLUSIONS

BNP and NT-proBNP measurements demonstrated assay-dependent correlations. Measurement of p-BNP or p-NT-proBNP by a two-site antibody assay demonstrated potential as an indicator of mild, incident HF, but the applicability of the index tests was limited over time and was likely influenced by therapeutic interventions.

B-type natriuretic peptides and echocardiographic measures of cardiac structure and function

Echocardiography and the B-type natriuretic peptides (BNPs) provide powerful incremental assessment of cardiac function, clinical status, and outcome across the spectrum of cardiac disease. There is strong evidence to support their integrated use in the diagnosis and management of cardiovascular disease. Amino-terminal pro-B-type natriuretic peptide (NT-proBNP) or BNP may guide more effective use of echocardiography in screening for asymptomatic left ventricular dysfunction; Doppler echocardiography improves the accuracy of heart failure diagnosis in the setting of intermediate BNP or NT-proBNP levels. Combined assessment of peptides and echocardiography provides more powerful stratification of risk across all stages of heart failure, and integrated use of both tests may identify subjects with valvular disease at greatest risk for progression and guide decision-making for timely intervention.

B-type natriuretic peptides and their relation to cardiovascular structure and function in a population-based sample of subjects aged 70 years

The aim of the present study was to evaluate whether B-type natriuretic peptides (BNPs) could serve as screening markers for the detection of preclinical vascular disease in the community. BNP and N-terminal-pro-BNP were analyzed in 1,000 subjects aged 70 years participating in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study and were related to different measures of endothelial function and activation, arterial compliance, carotid atherosclerosis, and echocardiographic findings. The median levels were 42.0 ng/L for BNP and 110.7 ng/L for N-terminal-pro-BNP. On adjusted multivariate analysis, the 2 BNPs were related to increased left ventricular mass and impaired left ventricular systolic and diastolic function but not to any of the other assessed entities reflecting preclinical vascular disease. In conclusion, BNPs are strong markers of increased left ventricular mass and impaired cardiac performance but cannot be regarded as useful screening markers for the detection of preclinical states of vascular disease in elderly subjects.

Amino-terminal pro-brain natriuretic peptid in prediction of left ventricular ejection fraction

We aimed to evaluate levels of amino-terminal pro-brain natriuretic peptid (NT-proBNP) in prediction of left ventricular ejection fraction (LVEF) in heart failure patients. Prospective study on 60 consecutive patients with symptoms and signs of heart failure was performed. Blood samples for NT-proBNP analysis was taken from all test subjects and echocardiography was also done in all of them. According to LVEF value, patients were divided into four groups; those with <or=30%, 31 to 39%, 40 to 49% and >or=50%. NT-proBNP values correlated with LVEF value. Regression analysis was used to evaluate how well NT-proBNP values predict LVEF. We used Receiver Operating Characteristic Curve calculation to evaluate diagnostic performance of NT-proBNP in estimation of LVEF. Average value of NT-proBNP in test group was 3191.69+/-642.89 pg/ml (p<0.001). Average value of NT-proBNP decreased with higher LVEF categories with significant (p<0.001) and high negative correlation (r= -0,75). Stepwise multivariate linear regression analysis showed that logarithmic value of NT-proBNP was excellent predictor of LVEF value (p<0.05). Model equation based on regression analysis was LVEF=88.645-15.311 x log (NT-proBNP). Predictive model for LVEF yielded from regression analysis had sensitivities of 98% and 81%, specificities of 20% and 90%, positive predictive values of 86% and 78% and negative predictive values of 67% and 92% for predicting patients with LVEF<50% and LVEF<40%, respectively. There was negative linear correlation between NT-proBNP and LVEF. NT-proBNP was excellent predictor of LVEF value (p<0.05).

Midregional pro-atrial natriuretic peptide is a useful indicator for the detection of impaired left ventricular function in patients with coronary artery disease

AIMS

We compared the diagnostic performance of N-terminal pro-brain natriuretic peptide (NT-proBNP) with a newly developed assay for the midregional part of pro-atrial natriuretic peptide (MR-proANP) concerning the detection of impaired left ventricular ejection function (LVEF) among patients with coronary artery disease (CAD).

METHODS AND RESULTS

Plasma levels of MR-proANP and NT-proBNP were determined in 102 consecutive patients with a history of ST-elevation myocardial infarction. Plasma levels of both markers were measured during a mean follow-up period of 687 days after acute myocardial infarction. Univariate analyses revealed inverse correlations between MR-proANP levels and LVEF (r=-0.39; p<0.001), NT-proBNP levels and LVEF (r=-0.39; p<0.001) and a positive correlation between MR-proANP and NT-proBNP (r=0.75; p<0.001). After adjustment for traditional risk factors, MR-proANP was the strongest predictor for LVEF (p=0.001) in multivariate analysis, being even superior to NT-proBNP. The area under the ROC curve (AUC) indicated moderate performance (AUC=0.73; p<0.01) of MR-proANP regarding the detection of a reduced LVEF<50%. The AUC of NT-proBNP for detection of impaired LVEF<50% was 0.68 (p=0.019). The negative predictive values of both markers were 86% for MR-proANP at a cut-off >135 pmol/L and NT-proBNP at a cut-off >560 pmol/L. At these cut-offs, the specificity of MR-proANP was 90%, and the specificity of NT-proBNP was 84%.

CONCLUSIONS

MR-proANP is a useful indicator for the exclusion of a preserved left ventricular function in patients with coronary artery disease. The study demonstrates that the diagnostic performance of MR-proANP is comparable to the "gold standard" NT-proBNP.

A glycosylated form of the human cardiac hormone pro B-type natriuretic peptide is an intrinsically unstructured monomeric protein

The N-terminal fragment of pro B-type natriuretic peptide (NT-proBNP) and proBNP are used as gold standard clinical markers of myocardial dysfunction such as cardiac hypertrophy and left ventricle heart failure. The actual circulating molecular forms of these peptides have been the subject of intense investigation particularly since these analytes are measured in clinical assays. Conflicting data has been reported and no firm consensus on the exact nature of the molecular species exists. Because these clinical assays are immunoassay-based, specific epitopes are detected. It is conceivable then that certain epitopes may be masked and therefore unavailable for antibody binding, thus the importance of determining the nature of the circulating molecular forms of these analytes. This situation is an unavoidable Achilles' heel of immunoassays in general. A recombinant O-linked glycosylated form of proBNP has been show to mimic some of the properties of extracted plasma from a heart failure patient. In particular the recombinant and native material co-migrated as diffuse Western-immunostained bands on SDS-PAGE and each band collapsed to an apparent homogeneous band following deglycosylation. Thus, glycosylated-proBNP may be one such circulating form. Here we provide extensive physiochemical characterization for this O-linked protein and compare these results to other described circulating species, non-glycosylated-proBNP and NT-proBNP. It will be shown that glycosylation has no influence on the secondary and quaternary structure of proBNP. In fact, at moderate concentration in benign physiological neutral pH buffer, all three likely circulating species are essentially devoid of major secondary structure, i.e., are intrinsically unstructured proteins (IUPs). Furthermore, all three proteins exist as monomers in solution. These results may have important implications in the design of NT-proBNP/BNP immunoassays.

Natriuretic peptides in cardiovascular diseases

The natriuretic peptide family comprises atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), dendroaspis natriuretic peptide (DNP), and urodilatin. The activities of natriuretic peptides and endothelins are strictly associated with each other. ANP and BNP inhibit endothelin-1 (ET-1) production. ET-1 stimulates natriuretic peptide synthesis. All natriuretic peptides are synthesized from polypeptide precursors. Changes in natriuretic peptides and endothelin release were observed in many cardiovascular diseases: e.g. chronic heart failure, left ventricular dysfunction and coronary artery disease.

Diagnostic accuracy of BNP and NT-proBNP in patients presenting to acute care settings with dyspnea: A systematic review

OBJECTIVE

We sought to compare the diagnostic performance of B-type natriuretic peptide (BNP) and N-terminal proBNP measurements in patients presenting to acute care settings with dyspnea, a common presenting symptom of heart failure.

DESIGN AND METHODS

We conducted a systematic review of the literature. For all included studies, we applied the QUADAS 14-question quality assessment tool for systematic reviews of diagnostic accuracy and abstracted the data for every published cut point.

RESULTS

We screened 4338 studies and included nine in the meta-analysis. All 9 studies scored positively on at least 50% of the QUADAS questions. The pooled estimates of sensitivity and specificity were the same for the BNP studies (0.97 (95% CI: 0.96, 0.98) and 0.70 (95% CI: 0.56, 0.85)) as for the NT-proBNP studies (0.95 (95% CI: 0.90, 1.01) and 0.72 (95% CI: 0.53, 0.90)). Tests for heterogeneity were significant in both subgroups: BNP (I(2)=97.9%, p<0.001) and NT-proBNP (I(2)=87.5%, p<0.001). Similar overall results were found for the likelihood and diagnostic odds ratios.

CONCLUSIONS

BNP and NT-proBNP have very similar diagnostic performance characteristics and can be used to rule out heart failure as a cause of dyspnea in the acute clinical setting. However, there is no easily identifiable optimum cut point value for each peptide.

Performance characteristics of the Architect brain natriuretic peptide (BNP) assay: a two site study

INTRODUCTION

Brain natriuretic peptide (BNP) is produced by the ventricles of the heart and is a biomarker for heart failure. Several commercial assays are now available. We evaluated the performance characteristics of the ARCHITECT BNP assay.

METHODS

We evaluated the limit of blank, limit of detection, linearity and imprecision. Method comparison studies were performed with 3 other automated BNP assays including the ADVIA Centaur, AxSYM, and UniCel DxI 800 methods.

RESULTS

The mean LOB and LOD of the Architect assay were 3.5 and 5.8 ng/L, respectively. Imprecision studies yielded within run CVs of 1.1 to 5.1% and total CVs of 2.3 to 5.3% using human plasma based multi-constituent controls at concentrations of 92, 500, and 3500 ng/L. The maximum deviation from the target recovery for dilution linearity was 9.6%. Concordance with other BNP assays at a 100 ng/l cutoff was 91 to 98% and kappa statistics were 0.78 to 0.96. The mean difference between the Architect and Advia Centaur methods was positive. For the other methods, the mean difference with the Architect was negative.

CONCLUSIONS

The Architect BNP assay shows good performance characteristics with total imprecision < or =5.3%. It agrees well with the Advia Centaur, AxSYM, and UniCel DxI BNP assays.

Amino-terminal pro-B-type natriuretic peptide testing for the diagnosis or exclusion of heart failure in patients with acute symptoms

When used for the evaluation of patients with acute symptoms in the emergency department setting, amino-terminal pro-B-type natriuretic peptide (NT-proBNP) testing is highly sensitive and specific for the diagnosis or exclusion of acute destabilized heart failure (HF), with results comparable to those reported for B-type natriuretic peptide (BNP) testing. When used for the diagnostic evaluation of the patient with possible HF, NT-proBNP testing returns information that may be superior to clinical judgment. However, the optimal application of NT-proBNP is in concert with history and physical examination, adjunctive testing, and with the knowledge of the differential diagnosis of an elevated NT-proBNP level. Studies indicate a dual use for NT-proBNP, both to exclude acute HF (where NT-proBNP concentrations <300 ng/L have a 98% negative predictive value), as well as to identify the diagnosis. To identify acute HF in patients with dyspnea, an age-independent NT-proBNP cut point of 900 ng/L has a similar value as that reported for a BNP value of 100 ng/L. However, age stratification of NT-proBNP using cut points of 450, 900, and 1,800 ng/L (for age groups of <50, 50-75, and >75 years) reduces false-negative findings in younger patients, reduces false-positive findings in older patients, and improves the overall positive predictive value of the marker without a change in overall sensitivity or specificity. Clinically validated, cost-effective algorithms for the use of NT-proBNP testing exist. Therefore, the logical use of NT-proBNP for the evaluation of the patient with suspected acute HF is useful, cost-effective, and may reduce adverse outcomes compared with standard clinical evaluation without natriuretic peptide testing.

Influence of left ventricular filling pattern on exercise-induced changes of natriuretic peptides in patients with suspected coronary artery disease

BACKGROUND

Exertional change in brain natriuretic peptide (BNP) has recently been proposed as a biomarker of myocardial ischemia. However, in patients with abnormal left ventricular (LV) filling, BNP is frequently increased. Therefore, we studied the relationship of exertional changes in atrial and brain natriuretic peptides (ANP and BNP) with resting and exercise-induced changes of LV systolic function and filling pattern.

METHODS

LV function at rest and peak exercise was assessed in 140 patients (mean age 65 years, 78 men) during symptom-limited exercise echocardiography for evaluation of suspected coronary artery disease. ANP and BNP were measured at rest and 5 min after exercise.

RESULTS

ANP and BNP increased with exercise. The increase in BNP was significantly greater in the 65 patients with than in the 76 patients without ischemia [14.7 pg/ml (5.7-19.6) vs. 4.9 pg/ml (2.1-9.2), p<0.0001]; there was no difference in increase of ANP [340 pg/ml (176-729) vs. 424 pg/ml (249-648), p=0.54]. The exertional rise in BNP was also greater in patients with abnormal LV filling at rest [10.5 pg/ml (4.9-19.6) vs. 4.1 pg/ml (2.0-6.7), p<0.0001]. By multivariate linear regression, exertional change in wall motion score index (beta=0.23, p<0.001), baseline BNP (beta=0.71, p<0.001), abnormal LV filling pattern (beta=0.24, p<0.001) and age (beta=-0.15, p=0.02) were predictors of change in BNP.

CONCLUSIONS

In patients with suspected coronary artery disease, exertional changes of BNP are related not only to ischemia, but also to the LV filling pattern at rest.

Analytical and clinical performance of three natriuretic peptide tests in the emergency room

BACKGROUND

The aim of the present study was to investigate the analytical and diagnostic utility of B-type natriuretic peptide (BNP) and the N-terminus of this prohormone, N-terminal pro-BNP (NT-pro-BNP) testing in the emergency department to identify acute congestive heart failure (CHF).

METHODS

A blood sample taken from patients presenting to the emergency department with acute dyspnoea (n=80) was analyzed for natriuretic peptides using three different assays [Triage BNP (Biosite), Centaur BNP (Bayer) and Elecsys NT-pro-BNP (Roche)]. A cardiologist and a pulmonologist, blinded to the actual natriuretic peptide levels, reviewed all test results (including echocardiography, etc.) retrospectively and made a diagnosis of dyspnoea due to CHF or not.

RESULTS

Analytical testing showed good correlation and coefficients of variation of less than 10% for all three assays. Cardiac-related dyspnoea was found in 40 patients (50%). NT-proBNP and BNP values were significantly elevated in these patients. For identifying patients with CHF, BNP and NT-proBNP scored equally well (area under the receiver operating characteristic curve of 0.78, 0.77 and 0.78 for the Biosite, Roche and Bayer assays, respectively).

CONCLUSIONS

In general, the different assays tested for BNP and NT-pro-BNP correlate very well in patients with suspected CHF and may aid in the risk stratification process in emergency departments. However, the value must always be interpreted in conjunction with other clinical information. It should also be considered that renal impairment can affect the results.

The use of biomarkers for the evaluation and treatment of patients with acute coronary syndromes

The advent of inexpensive, highly accurate, and predictive markers of myocardial injury, inflammation, and hemodynamic stability has revolutionized the evaluation and treatment of patients who have acute coronary syndromes (ACSs). These blood biomarkers require small sample volumes, can be run expeditiously, and provide important information concerning the diagnosis, risk stratification, and treatment of these patients. To understand the use of these markers, one must have some knowledge about what elevations in these markers imply, how they have to be collected and measured to provide reliable information, when to suspect analytic confounds, and what the key values are that impart the diagnostic, prognostic, and therapeutic information. This article discusses these issues, emphasizing what clinicians must know for optimal test use, and then addresses the practical use of these markers in patients who have ACS.

Comparison of the clinical utility of atrial and B type natriuretic peptide measurement for the diagnosis of systolic dysfunction in a low-risk population

BACKGROUND

Measurement of B type natriuretic peptide and its N terminal prohormone (NTproBNP) can now be performed routinely by automated high-throughput immunoassays. The study compared measurement of NTproBNP with measurement of N terminal pro-atrial natriuretic peptide (NTproANP) for detection of ventricular systolic dysfunction in primary care.

METHODS

734 subjects aged >45 years (349 men and 385 women, median age 58 years, range 45-89, interquartile range 51-67 years) from seven representative general practices attended for echocardiography with determination of ejection fraction and completed a questionnaire. Blood samples were collected into gel serum separation tubes (Becton-Dickinson, Franklin Lakes, New Jersey, USA), the serum separated and aliquots stored frozen at -70 degrees C until analyses. Samples were analysed for NTproBNP (Roche Diagnostics, Lewes, UK; coefficient of variation (CV) 3.2-2.4%) and for NTproANP (Biomedica, Vienna, Austria; CV 5.6-10.1%). Echocardiography was used as the diagnostic "gold standard", with ventricular systolic dysfunction defined as abnormal when there was an ejection fraction of <or=40%. Patients were dichotomised by ejection fraction from 50% to 30%, and receiver operating characteristic curves constructed and the area under the curve (AUC) compared.

RESULTS

At 40% ejection fraction, NTproANP and NTproBNP showed AUCs of, respectively, 0.738 (0.601-0.875) and 0.973 (0.958-0.989), p<0.004.

CONCLUSION

NTproBNP is superior to NTproANP for detection of systolic dysfunction.

Comparison of brain natriuretic peptide (BNP) and amino-terminal ProBNP for early diagnosis of heart failure

BACKGROUND

We compared the diagnostic accuracy of brain natriuretic peptide (BNP) and amino-terminal proBNP (NT-proBNP) for diagnosis of preclinical and mild heart failure (HF).

METHODS

We assayed plasma NT-proBNP and BNP in 182 healthy controls and in a prospective cohort of 820 HF patients divided according to the American Heart Association/American College of Cardiology classification. These included 86 patients in stage A [mean (SE) ejection fraction 61% (1%); mean (SE) age 47 (2) years], 255 in stage B [65% (2%); 62 (1) years], 420 patients in stage C [35% (1%); 68 (1) years] and 59 in stage D [25% (1%); 74 (1) years]. Diagnostic accuracies of BNP and NT-proBNP were evaluated by ROC analysis, and a multivariate linear regression model was applied to predict HF staging.

RESULTS

Median BNP and NT-proBNP concentrations increased from stage A to D 57-fold and 107-fold, respectively. Both assays were accurate (P <0.001) in separating stage B from controls or stage A, and stage C from controls or stage A or B. NT-proBNP was more accurate (P <0.001) than BNP in differentiating stage C from stages A and B patients and controls and was a better predictor of HF classification in a model including age, sex, and renal function (P <0.001).

CONCLUSIONS

Monitoring BNP or NT-proBNP enabled identification of asymptomatic patients at risk for the development of HF. NT-proBNP showed better accuracy than BNP for identifying mild HF.

The human cardiac hormone fragment N-terminal pro B-type natriuretic peptide is an intrinsically unstructured protein

The cardiac hormone B-type natriuretic peptide (BNP) is synthesized as a prepro 134 residue molecule which is further proteolytically processed into a 76 residue fragment termed N-terminal proBNP (NT-proBNP) and the active portion of this hormone, a 32-residue disulfide-linked peptide (BNP-32). The active hormone regulates cardiac hemodynamic output while as yet no biological function has been attributed to NT-proBNP. Some solution properties of synthetically generated NT-proBNP in benign media are known. The protein is monomeric, elutes aberrantly on size-exclusion chromatography as an apparent larger molecular species, and possesses little global secondary structure as assessed by circular dichroism. To explore the solution structure of NT-proBNP in greater detail, we use 2D-NOESY and 2D-TOCSY NMR on recombinant NT-proBNP to obtain a high resolution solution conformation at the alpha-carbon level. Importantly, NH(i)-NH(i+1) coupling is virtually absent at room temperature implying that large stretches of primary sequence are unordered. Together, the results of these physicochemical measurements classify NT-proBNP as a naturally unfolded protein referred to as an Intrinsically Unstructured Protein (IUP). The calculations of FoldIndex, a computer program which predicts disorder, were compared to the experimental results described here for NT-proBNP in addition to proBNP. NT-proBNP thus appears to be an ideal candidate for the study of native, unfolded proteins.

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

Background: We used evidence-based laboratory medicine principles to compare the diagnostic accuracy of brain natriuretic peptide (BNP) and the N-terminal part of the propeptide of BNP (NT-proBNP) assays for the diagnosis of heart failure.

Methods: In May 2006, we performed a computerized literature search of the online National Library of Medicine to select studies specifically designed to compare the diagnostic accuracy of BNP and NT-proBNP assays. The comparison took into account the area under the curve and diagnostic odds ratio (DOR) derived from ROC analysis of original studies.

Results: Both BNP and NT-proBNP assays were found to be clinically useful for the diagnosis of heart failure. Metaanalysis of these data was difficult because of the heterogeneity of data regarding patient population, diagnostic criteria, end-points, and immunoassay methods for both BNP and NT-proBNP. Separate metaanalyses were performed for acute and chronic heart failure. In chronic heart failure, the diagnostic DOR for BNP (8.44, 95% CI 4.66–15.30) was not significantly different from that of NT-proBNP (23.36, 95% CI 9.38–58.19). In patients with acute heart failure, the mean DOR for BNP (16.46, 95% CI 10.65–25.43) was not significantly different from that of NT-proBNP (18.61, 95% CI 12.99–26.65).

Conclusion: Our results indicate that both BNP and NT-proBNP assays have a high degree of diagnostic accuracy and clinical relevance for both acute and chronic heart failure.

Hyperhomocysteinemia and Myocardial Expression of Brain Natriuretic Peptide in Rats

Background: Hyperhomocysteinemia (HHcy) has been linked to impaired left ventricular function and clinical class in patients with chronic heart failure. We hypothesized that HHcy stimulates myocardial brain natriuretic peptide (BNP) expression and induces adverse left ventricular remodeling.

Methods: We randomized 50 rats into 5 groups. Groups Co1 and Co2 (controls) received a typical diet. Groups Meth, Hcy1, and Hcy2 were fed the same diet supplemented with 2.4% methionine, 1% homocystine, and 2% homocystine, respectively. After 12 weeks, we measured total plasma homocysteine (tHcy) and BNP in plasma and tissue, and we performed histomorphometric analyses.

Results: All animals had comparable baseline body weight [mean (SD) 234 (26) g] and total circulating Hcy [4.7 (1.7) μmol/L]. After 12 weeks of treatment, total circulating Hcy increased in Meth, Hcy1, and Hcy2 [27.3 (8.8), 40.6 (7.0), and 54.0 (46.0) μmol/L, respectively] and remained unchanged in Co1 and Co2. Serum BNP significantly increased in 1 of 10 animals in Meth, 3 of 10 animals in Hcy1, and 3 of 10 animals in Hcy2. Median (25th–75th percentile) BNP tissue concentrations in Hcy1 and Hcy2 were 55% higher than in the corresponding controls [Co1 vs Hcy1, 225 (186–263) vs 338 (262–410) pg/mg protein, P = 0.05; Co2 vs Hcy2, 179 (107–261) vs 308 (192–429) pg/mg protein, P = 0.12]. In the Meth group, BNP expression was comparable to that of controls [200 (159–235) vs 225 (186–263) pg/mg protein, P = 0.32]. The percentage of perivascular and interstitial collagen and mast cell infiltration were comparable in all groups, indicating no adverse cardiac remodeling.

Conclusion: Three months of intermediate HHcy stimulated increased cardiac BNP expression that was not accompanied by adverse cardiac remodeling.

3-week hiking holidays at moderate altitude do not impair cardiac function in individuals with metabolic syndrome

We studied the influence of a 3-week hiking vacation at moderate altitude on cardiac pump and endocrine function. 18 males (mean age: 55 years, range 36-60) with metabolic syndrome participated in a 3-week structured guided hiking vacation program (4 times per week at 55-65% of maximal heart rate, total exercise time 29 h). Echocardiography, B-type natriuretic peptide (BNP), NT-proBNP, and endothelin-1 measurements were performed at baseline in Innsbruck (576 m a.s.l., Austria), on the first day at moderate altitude (Obertauern, 1700 m a.s.l., Austria), after 3 weeks in Obertauern, and at follow-up in Innsbruck. We found no adverse cardiovascular effects and no significant changes in echocardiographic measures of systolic or diastolic function, estimated systolic pulmonary artery pressure, exercise capacities, BNP and NT-proBNP, or endothelin-1 concentrations. The blood pressure at rest significantly decreased from baseline to follow-up.