Specificity of B-Type Natriuretic Peptide Assays: Cross-Reactivity with Different BNP, NT-proBNP, and proBNP Peptides

NT-proBNP-Possible Prognostic Marker in Pregnant Patients with Associated Cardiovascular Risk Factors and SARS-CoV-2 Infection

BACKGROUND

N-terminal pro brain-type natriuretic peptide (NT-proBNP) is a practical biomarker in the clinical pathologies where the ventricle is under stress and particularly stretched in the general population. The study aims to compare the value of NT-proBNP and its importance in the prognosis and severity of the cases involving pregnant patients with SARS-CoV-2 infection and cardiovascular risk factors to those of low-risk pregnant patients, mainly by analysing their symptoms, administered medication, days of hospitalization and severity of the viral disease.

METHODS

The study included a total of eighty-three pregnant patients who underwent natural birth or caesarean section at out hospital. NT-proBNP levels were analyzed at hospital admission as a potential cardiovascular marker. A comparative analysis was performed between pregnant patients with cardiovascular risk factors and pregnant patients without cardiovascular risk factors regarding NT-proBNP values.

RESULTS

Pregnant patients with SARS-CoV-2 infection and cardiovascular risk factors had higher values of NT-proBNP in comparison to pregnant patients without cardiovascular risk factors.

CONCLUSIONS

NT-proBNP testing in pregnant patients with SARS-CoV-2 infection can be a relatively important marker to be taken into consideration when it comes to the management, treatment and outcome of the cases, especially when it comes to women with associated cardiovascular risk factors.

Selection, alkaline phosphatase fusion, and application of single-chain variable fragment (scFv) specific to NT-proBNP as electrochemical immunosensor for heart failure

Heart failure has a high global prevalence, with symptoms such as breathlessness, fatigue, and swelling. Early detection is crucial, as the condition worsens over time and can be fatal. This study identified the single-chain variable fragment (scFv) that specifically binds to the heart failure biomarker N-terminal pro B-type natriuretic peptide (NT-proBNP) using biopanning techniques for the development of an alternative diagnostic tool. Ten clones were identified that bound to the target peptide, with two clones (scFv-16 and scFv-36) selected for further analysis. Soluble scFv-16 and scFv-36 were produced and fused with alkaline phosphatase (AP) for potential applications. The binding efficiency and specificity levels of scFv to natriuretic peptides were evaluated using surface plasmon resonance (SPR) analysis. The values of the dissociation constant (KD) for NT-proBNP of scFv-16, scFv-36, scFv-16-AP, and scFv-36-AP were in the range 3.72 × 10-7-3.42 × 10-8 M with high specificity. All constructed scFvs had specificity to NT-proBNP, while not binding to A-type (ANP) and C-type (CNP) natriuretic peptides. When AP was combined, the scFv had a slightly higher yield of expression. The enzyme activity of scFv-36-AP was observed first by the absorption at 405 nm at a minimum of 44 nM and then by the naked eye at a minimum of 88 nM. Additionally, the potential application of NT-proBNP binding scFv was preliminarily investigated using an electrochemical technique to directly detect NT-proBNP in phosphate buffer saline. The results revealed the limit of detection at 69.09 pg/mL, which was less than the cutoff value (150 pg/mL) to discharge patients or healthy people. These findings provided promising biomolecules for the development of a reliable and sensitive diagnostic tool for heart failure.

HiSorb sorptive extraction for determining salivary short chain fatty acids and hydroxy acids in heart failure patients

Variations in salivary short-chain fatty acids and hydroxy acids (e.g., lactic acid, and 3-hydroxybutyric acid) levels have been suggested to reflect the dysbiosis of human gut microbiota, which represents an additional factor involved in the onset of heart failure (HF) disease. The physical-chemical properties of these metabolites combined with the complex composition of biological matrices mean that sample pre-treatment procedures are almost unavoidable. This work describes a reliable, simple, and organic solvent free protocol for determining short-chain fatty acids and hydroxy acids in stimulated saliva samples collected from heart failure, obese, and hypertensive patients. The procedure is based on in-situ pentafluorobenzyl bromide (PFB-Br) derivatization and HiSorb sorptive extraction coupled to thermal desorption and gas chromatography-tandem mass spectrometry. The HiSorb extraction device is completely compatible with aqueous matrices, thus saving on time and materials associated with organic solvent-extraction methods. A Central Composite Face-Centred experimental design was used for the optimization of the molar ratio between PFB-Br and target analytes, the derivatization temperature, and the reaction time which were 100, 60 °C, and 180 min, respectively. Detection limits in the range 0.1-100 µM were reached using a small amount of saliva (20 µL). The use of sodium acetate-1-13C as an internal standard improved the intra- and inter-day precision of the method which ranged from 10 to 23%. The optimized protocol was successfully applied for what we believe is the first time to evaluate the salivary levels of short chain fatty acids and hydroxy acids in saliva samples of four groups of patients: i) patients admitted to hospital with acute HF symptoms, ii) patients with chronic HF symptoms, iii) patients without HF symptoms but with obesity, and iv) patients without HF symptoms but with hypertension. The first group of patients showed significantly higher levels of salivary acetic acid and lactic acid at hospital admission as well as the lowest values of hexanoic acid and heptanoic acid. Moreover, the significant high levels of acetic acid, propionic acid, and butyric acid observed in HF respect to the other patients suggest the potential link between oral bacteria and gut dysbiosis.

Lot-to-Lot Variance in Immunoassays-Causes, Consequences, and Solutions

Immunoassays, which have gained popularity in clinical practice and modern biomedical research, play an increasingly important role in quantifying various analytes in biological samples. Despite their high sensitivity and specificity, as well as their ability to analyze multiple samples in a single run, immunoassays are plagued by the problem of lot-to-lot variance (LTLV). LTLV negatively affects assay accuracy, precision, and specificity, leading to considerable uncertainty in reported results. Therefore, maintaining consistency in technical performance over time presents a challenge in reproducing immunoassays. In this article, we share our two-decade-long experience and delve into the reasons for and locations of LTLV, as well as explore methods to mitigate its effects. Our investigation identifies potential contributing factors, including quality fluctuation in critical raw materials and deviations in manufacturing processes. These findings offer valuable insights to developers and researchers working with immunoassays, emphasizing the importance of considering lot-to-lot variance in assay development and application.

Diagnostic utility of total NT-proBNP testing by immunoassay based on antibodies targeting glycosylation-free regions of NT-proBNP

OBJECTIVES

The N-terminal fragment of pro-B-type natriuretic peptide (NT-proBNP) is a widely used heart failure (HF) biomarker. Commercial NT-proBNP immunoassays detect only a subfraction of endogenous NT-proBNP, as the antibodies target a region of NT-proBNP that could be glycosylated at Ser44. The diagnostic utility of immunoassays measuring total NT-proBNP remains unclear.

METHODS

NT-proBNP was measured in 183 HF and 200 non-HF patients diagnosed by two independent cardiologists blinded to NT-proBNP results. Plasma samples either non-treated or treated with a mixture of glycosidases were analyzed by the Elecsys proBNP II assay (Roche Diagnostics, based on antibodies targeting a glycosylated region of NT-proBNP) and the SuperFlex NT-proBNP assay (PerkinElmer, based on antibodies targeting regions of NT-proBNP that are free of O-glycans). The diagnostic accuracy of the two assays was analyzed by comparison of ROC curves.

RESULTS

The ROC-AUC for the proBNP II assay was 0.943 (95% CI 0.922-0.964) for NT-proBNP measured in untreated samples and 0.935 (0.913-0.958) for NT-proBNP measured in glycosidase-treated samples. The SuperFlex NT-proBNP assay in untreated samples gave a ROC-AUC of 0.930 (95% CI 0.907-0.954). The median percentage of non-glycosylated NT-proBNP to total NT-proBNP was 1.5-1.6-fold lower in the non-HF group compared to that in the HF group.

CONCLUSIONS

The clinical value of total NT-proBNP for HF diagnosis was similar to the subfraction of NT-proBNP that was non-glycosylated at Ser44. The lower percentage of non-glycosylated NT-proBNP to total NT-proBNP in non-HF patients suggests that total NT-proBNP might be more sensitive in individuals without current or prior symptoms of HF.

Deconvolution of BNP and NT-proBNP Immunoreactivities by Mass Spectrometry in Heart Failure and Sacubitril/Valsartan Treatment

BACKGROUND

Elevated BNP and the N-terminal fragment of the proBNP (NT-proBNP) are hallmarks of heart failure (HF). Generally, both biomarkers parallel each other. In patients receiving sacubitril/valsartan, BNP remained stable while NT-proBNP decreased. As BNP and NT-proBNP assays have limited specificity due to cross-reactivity, we quantified by mass spectrometry (MS) the contributing molecular species.

METHODS

We included 356 healthy volunteers, 100 patients with acute dyspnoea (49 acute decompensated HF; 51 dyspnoea of non-cardiac origin), and 73 patients with chronic HF and reduced ejection fraction treated with sacubitril/valsartan. BNP and NT-proBNP immunoreactivities (BNPir and NT-proBNPir) were measured by immunoassays (Abbott ARCHITECT and Roche Diagnostics proBNPII) and proBNP-derived peptides and glycosylation at serine 44 by MS on plasma samples.

RESULTS

BNPir corresponded to the sum of proBNP1-108, BNP1-32, BNP3-32, and BNP5-32 (R2 = 0.9995), while NT-proBNPir corresponded to proBNP1-108 and NT-proBNP1-76 not glycosylated at serine 44 (R2 = 0.992). NT-proBNPir was better correlated (R2 = 0.9597) than BNPir (R2 = 0.7643) with proBNP signal peptide (a surrogate of proBNP production). In patients receiving sacubitril/valsartan, non-glycosylated NT-proBNP1-76 remained constant (P = 0.84) despite an increase in NT-proBNP1-76 and its glycosylation (P < 0.0001). ProBNP1-108 remained constant (P = 0.12) while its glycosylation increased (P < 0.0001), resulting in a decrease in non-glycosylated proBNP1-108 (P < 0.0001), and in NT-proBNPir.

CONCLUSIONS

Glycosylation interfered with NT-proBNPir measurement, explaining the discrepant evolution of these 2 biomarkers in patients receiving sacubitril/valsartan. Both BNPir and NT-proBNPir are surrogates of proBNP1-108 production, NT-proBNPir being more robust in the clinical contexts studied.

Correlation between urinary and serum NT-proBNP in acute bronchiolitis: A pilot study

BACKGROUND AND AIMS

We aimed to analyze the correlation of urinary with serum N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations and its association with severity in acute bronchiolitis.

MATERIAL AND METHODS

A pilot observational study was conducted between October 1, 2021 and March 31, 2022 including acute bronchiolitis cases who attended our institution. Serum and urinary NT-proBNP concentrations were determined using the Alere i NT-proBNP assay in time-matched urine and blood samples. The Mann-Whitney U test, Spearman's correlations, and simple linear regression were utilized to analyze the association of urine NT-proBNP levels with serum NT-proBNP and with variables indicative of severe bronchiolitis.

RESULTS

Seventeen infants (median age 68 [IQR: 36-91] days) with 36 time-matched samples were included. The urine NT-proBNP was positively and strongly correlated with the serum NT-proBNP concentrations (Spearman's ρ = 0.81 & R2  coefficient = 0.751; p < 0.001), and increased with higher C-reactive protein, (p = 0.004), procalcitonin (p = 0.001), and pCO2 (p = 0.029) levels. The initial urinary NT-proBNP concentrations were higher in those infants that required ventilatory support compared with those without this outcome (1.85 [IQR: 1.16-2.44] vs. 0.63 [IQR: 0.45-0.84] pg/mg); p < 0.001); and resulted positively and strongly correlated with the duration of the ventilatory support (Spearman's ρ = 0.76; p < 0.001) and the length of stay hospitalization (Spearman's ρ = 0.84; p < 0.001).

CONCLUSION

The urinary NT-proBNP concentrations could be a reliable surrogate for serum NT-proBNP levels and resulted elevated in cases of acute bronchiolitis with complicated evolution, suggesting a potential as a noninvasive tool to assess severity in this setting.

Assays Specific for BNP1-32 and NT-proBNP Exhibit a Similar Performance to Two Widely Used Assays in the Diagnosis of Heart Failure

BACKGROUND

Secretion of cardioprotective B-type natriuretic peptide 1-32 (BNP1-32) is increased proportionately with cardiac dysfunction, but its measurement in plasma is difficult. Therefore, less specific BNP and amino-terminal proBNP (NT-proBNP) assays that detect the precursor molecule proBNP alongside BNP or NT-proBNP metabolites were developed to reflect BNP1-32 secretion and are now mandated in the diagnosis of heart failure (HF). We compared the diagnostic performance of 2 widely used clinical assays: the Roche proBNPII assay, and Abbott BNP assay, against our recently developed in-house assays that measure either intact BNP1-32 or NT-proBNP.

METHODS

EDTA plasma samples obtained from patients presenting with breathlessness (n = 195, 60 [31%] with clinically adjudicated HF) were assayed using the Roche NT-proBNP and our specific in-house BNP1-32 and NTBNP assays. A subset (n = 75) were also assessed with the Abbott BNP assay.

RESULTS

Roche NT-proBNP was highly correlated with BNP1-32 and NTBNP (Spearman rho = 0.92 and 0.90, respectively, both Ps < 0.001), and all 3 assays similarly discriminated acute HF from other causes of breathlessness (ROC analysis areas under the curve 0.85-0.89). The Abbott BNP assay performed similarly to the other assays. Roche NT-proBNP and BNP1-32 assays had similar sensitivity (83% and 80%), specificity (83% and 84%), positive (70% and 71%) and negative (91% and 90%) predictive values, and accuracy (both 83%) at their optimal cutoffs of 1536 and 12 ng/L, respectively.

CONCLUSIONS

Since all assays exhibited similar performance in the diagnosis of HF, currently mandated assays provide a reliable proxy for circulating concentrations of active BNP1-32 in HF diagnosis.

The effect of GLP-1 receptor agonists on N-terminal pro-brain natriuretic peptide. A scoping review and metanalysis

AIMS

Glucagon-like peptide 1 receptor agonists (GLP-1RA) decrease the risk of major adverse cardiovascular events (MACE). However, their influence on the risk of heart failure (HHF) hospitalization is marginal, which is unexpected given their benefits on cardiometabolic risk, especially on bodyweight reduction. This meta-analysis aimed to map the effects of GLP-1RA on N-terminal pro-BNP.

METHODS AND RESULTS

We retrieved from a Medline and Embase all randomized trials comparing GLP-1RA with placebo, reporting NT-proBNP concentrations. The primary outcome was the change in N-terminal pro-BNP values from baseline to end-of-treatment with GLP-1RA versus placebo (reported as standard deviations, SD). We included nine trials (543 patients in active treatment and 536 in placebo). We observed significantly greater reductions in N-terminal pro-BNP with GLP-1RA versus placebo (-0.14 SD; 95% CI -0.27; -0.01; p = 0.03). Upon meta-regression, no modifying effect of age, HbA1c, and body mass index were observed, nor was any meta-correlation between the change in NT-proBNP and the change in HbA1c or body weight.

CONCLUSIONS

GLP-1RA can significantly decrease N-terminal pro-BNP. This effect was independent of baseline age, body weight, and metabolic control.

Point-of-care NT-proBNP monitoring for heart failure: observational feasibility study in primary care

Background

Around one million individuals in the UK have heart failure (HF), a chronic disease that causes significant morbidity and mortality. N-terminal pro-B-type natriuretic peptide (NT-proBNP) monitoring could help improve the care of patients with HF in the community.

Aim

The aim of this study is to provide evidence to support the routine use of point-of-care (POC) NT-proBNP monitoring in primary care.

Design & setting

In this observational cohort study, the Roche Cobas h 232 POC device was used to measure NT-proBNP in 27 patients with HF at 0, 6, and 12 months, with a subset reanalysed in the laboratory for comparison.

Method

Data were analysed for within-person and between-person variability and concordance with laboratory readings using Passing–Bablok regression. GPs reported whether POC results impacted clinical decisionmaking, and patients indicated their willingness to participate in long-term cohort studies using the Likert acceptability scale.

Results

Within-person variability in POC NT-proBNP over 12 months was 881 pg/mL (95% confidence interval [CI] = 380 to 1382 pg/mL). Between-person variability was 1972 pg/mL (95% CI = 1,525 to 2791 pg/mL). Passing–Bablok regression showed no significant systematic difference between POC and laboratory measurements. Patients indicated a high level of acceptability, and GP decisionmaking was affected for at least one visit in a third of patients.

Conclusion

Within-person variability in POC NT-proBNP is around half of between-person variability, so detecting changes could be of use in HF management. High patient acceptability and impact on clinical decisionmaking warrant further investigation in a larger long-term cohort study.

Total NT-proBNP, a novel biomarker related to recurrent atrial fibrillation

Background

Novel circulating biomarkers may help in understanding the underlying mechanisms of atrial fibrillation (AF), a challenge for AF management and prevention of cardiovascular (CV) events. Whether glycosylation affects the prognostic value of N-terminal pro-B type natriuretic peptide (NT-proBNP) in AF is still unknown.

Objectives

To test how deglycosylated total NT-proBNP, NT-proBNP and a panel of biomarkers are associated with: (1) recurrent AF, (2) first hospitalization for CV reasons.

Methods

A total of 382 patients of the GISSI-AF trial in sinus rhythm with a history of AF, echocardiographic variables, total NT-proBNP, NT-proBNP and nine additional biomarkers [Total N-terminal pro-B type natriuretic peptide (Total NT proBNP), N-terminal pro-B type natriuretic peptide (NTproBNP), Angiopoietin 2 (Ang2), Bone morphogenic protein-10 (BMP10), Dickkopf-related protein-3 (DKK3), Endothelial cell specific molecule-1 (ESM1), Fatty acid-binding protein 3 (FABP3), Fibroblast growth factor 23 (FGF23), Growth differentiation factor-15 (GDF15), Insulin-like growth factor-binding protein-7 (IGFBP7) and Myosin binding protein C3 (MYPBC3)]. were assayed at baseline, 6 and 12 months under blind conditions in a laboratory at Roche Diagnostics, Penzberg, Germany. The associations between circulating biomarkers and AF at the 6- and 12-month visits, and their predictive value, were assessed in multivariable models with logistic regression analysis and Cox proportional hazards regression analysis. Biomarkers associations were modelled for 1SD increase in their level.

Results

Over a median follow-up of 365 days, 203/382 patients (53.1%) had at least one recurrence of AF and 16.3% were hospitalized for CV reasons. Total NT-proBNP, NT-proBNP, Ang2 and BMP10 showed the strongest associations with ongoing AF. Natriuretic peptides also predicted recurrent AF (total NT-proBNP: HR:1.19[1.04–1.36], p = 0.026; NT-proBNP: HR:1.19[1.06–1.35], p = 0.016; Ang2: HR:1.07[0.95–1.20], p = 0.283; BMP10: HR:1.09[0.96–1.25], p = 0.249) and CV hospitalization (total NT-proBNP: HR:1.57[1.29–1.90], p < 0.001 1.63], p = 0.097).

Conclusions

The association of total NT-proBNP with the risk of AF first recurrence was similar to that of NT-proBNP, suggesting no influence of glycosylation. Analogous results were obtained for the risk of first hospitalization for CV reasons. Natriuretic peptides, Ang2 and BMP10 were associated with ongoing AF. Findings from the last two biomarkers point to a pathogenic role of cardiac extracellular matrix and cardiomyocyte growth in the myocardium of the right atrium and ventricle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02358-y.

NT-proBNP/BNP ratio for prognostication in European Caucasian patients enrolled in a heart failure prevention programme

Aims

Guidelines support the role of B‐type natriuretic peptide (BNP) and amino‐terminal pro‐BNP (NT‐proBNP) for risk stratification of patients in programmes to prevent heart failure (HF). Although biologically formed in a 1:1 ratio, the ratio of NT‐proBNP to BNP exhibits wide inter‐individual variability. A report on an Asian population suggests that molar NT‐proBNP/BNP ratio is associated with incident HF. This study aims to determine whether routine, simultaneous evaluation of both BNP and NT‐proBNP is warranted in a European, Caucasian population.

Methods and Results

We determined BNP and NT‐proBNP levels for 782 Stage A/B HF patients in the STOP‐HF programme. The clinical, echocardiographic, and biochemical associates of molar NT‐proBNP/BNP ratio were analysed. The primary endpoint was the adjusted association of baseline molar NT‐proBNP/BNP ratio with new‐onset HF and/or progression of left ventricular dysfunction (LVD). We estimated the C‐statistic, integrated discrimination improvement, and the category‐free net reclassification improvement metric for the addition of molar NT‐proBNP/BNP ratio to adjusted models. The median age was 66.6 years [interquartile range (IQR) 59.5–73.1], 371 (47.4%) were female, and median molar NT‐proBNP/BNP ratio was 1.91 (IQR 1.37–2.93). Estimated glomerular filtration rate, systolic blood pressure, left ventricular mass index, and heart rate were associated with NT‐proBNP/BNP ratio in a linear regression model (all P < 0.05). Over a median follow‐up period of 5 years (IQR 3.4–6.8), 247 (31.5%) patients developed HF or progression of LVD. Log‐transformed NT‐proBNP/BNP ratio is inversely associated with HF and LVD risk when adjusted for age, gender, diabetes, hypertension, vascular disease, obesity, heart rate, number of years of follow‐up, estimated glomerular filtration rate, and baseline NT‐proBNP (odds ratio 0.71, 95% confidence interval 0.55–0.91; P = 0.008). However, molar NT‐proBNP/BNP ratio did not increase the C‐statistic (Δ −0.01) and net reclassification improvement (0.0035) for prediction of HF and LVD compared with NT‐proBNP or BNP alone. Substitution of NT‐proBNP for BNP in the multivariable model eliminated the association with HF and LVD risk.

Conclusions

This study characterized, for the first time in a Caucasian Stage A/B HF population, the relationship between NT‐proBNP/BNP ratio and biological factors and demonstrated an inverse relationship with the future development of HF and LVD. However, this study does not support routine simultaneous BNP and NT‐proBNP measurement in HF prevention programmes amongst European, Caucasian patients.

Prognostic Value of Natriuretic Peptides for All-Cause Mortality, Right Ventricular Failure, Major Adverse Events, and Myocardial Recovery in Advanced Heart Failure Patients Receiving a Left Ventricular Assist Device: A Systematic Review

Aims: Major adverse event (MAE) rates during left ventricular assist device (LVAD) therapy in advanced heart failure (HF) patients are high, and impair quality of life and survival. Prediction and risk stratification of MAEs in order to improve patient selection and thereby outcome during LVAD therapy is therefore warranted. Circulating natriuretic peptides (NPs) are strong predictors of MAEs and mortality in chronic HF patients. However, whether NPs can identify patients who are at risk of MAEs and mortality or tend toward myocardial recovery after LVAD implantation is unclear. The aim of this systematic review is to analyze the prognostic value of circulating NP levels before LVAD implantation for all-cause mortality, MAEs and myocardial recovery after LVAD implantation.

Methods and Results: Electronic databases were searched for studies analyzing circulating NP in adults with advanced HF before LVAD implantation in relation to mortality, MAEs, or myocardial recovery after LVAD implantation. Twenty-four studies published between 2008 and 2021 were included. Follow-up duration ranged from 48 hours to 5 years. Study sample size ranged from 14 to 15,138 patients. Natriuretic peptide levels were not predictive of all-cause mortality. However, NPs were predictive of right ventricular failure (RVF) and MAEs such as ventricular arrhythmias, moderate or severe aortic regurgitation, and all-cause rehospitalization. No relation between NPs and myocardial recovery was found.

Conclusion: This systematic review found that NP levels before LVAD implantation are not predictive of all-cause mortality after LVAD implantation. Thus, NP levels may be of limited value in patient selection for LVAD therapy. However, NPs help in risk stratification of MAEs and may be used to identify patients who are at risk for RVF, ventricular arrhythmias, moderate or severe aortic regurgitation, and all-cause rehospitalization after LVAD implantation.

Active B-Type Natriuretic Peptide Measured by Mass Spectrometry and Response to Sacubitril/Valsartan

BACKGROUND

B-type natriuretic peptide (BNP) immunoassays (BNP_ia) do not differentiate active and inactive forms. Inactive NT-proBNP is used to track heart failure (HF) during treatment with sacubitril/valsartan, which inhibits BNP degradation. Mass spectrometry (MS) may better assess effects of HF treatment on biologically active BNP1-32.

METHODS AND RESULTS

We developed a MS assay with immediate protease inhibition to quantify BNP1-32 over a linear range, using labeled recombinant BNP standard. In 4 healthy volunteers, BNP1-32 by MS (BNP_MS) increased from below the 5 pg/mL detection limit to 228 pg/mL after nesiritide. In patients with HF, BNP_MS was measured in parallel with BNP and NT-proBNP immunoassays before and during sacubitril/valsartan treatment. BNP_MS was 4.4-fold lower than BNP_ia in patients with HF. Among patients not taking sacubitril/valsartan and without end-stage renal disease, BNP_MS correlated with BNP_ia (r_s = 0.77, P < .001) and NT-proBNP (r_s = 0.74, P < .001). After a median of 8 weeks on sacubitril/valsartan, active BNP_MS levels decreased by 50% (interquartile range -98.3% to 41.7%, n = 22, P = .048) and correlated with NT-proBNP (r_s = 0.64, P < .001), but not with BNP_ia (r_s = 0.46, P = .057).

CONCLUSIONS

Active BNP measured by MS accounts for only a small amount of BNP measured by immunoassays. Although decreased BNP production was anticipated to be masked by inhibition of degradation, levels of active BNP decreased during chronic sacubitril/valsartan treatment.

Exposing the High Heterogeneity of Circulating Pro B-Type Natriuretic Peptide Fragments in Healthy Individuals and Heart Failure Patients

BACKGROUND

The high molecular complexity of variably O-glycosylated and degraded pro B-type natriuretic peptide (proBNP) derived molecular forms challenges current immunoassays. Antibodies used show pronounced differences in cross-reactivities with these circulating fragments, which still need to be better characterized on a molecular level. To pave the way for advanced quantitative assays in the future, it is critical to fully understand these circulating forms.

METHODS

Plasma samples were collected from 8 heart failure (HF) patients and 2 healthy controls. NT-proBNP and proBNP were purified by immunoprecipitation and analyzed by nano-flow liquid chromatography coupled to high-resolution mass spectrometry. Fragments formed during proteolysis in solution digestion were distinguished from naturally occurring peptides by using an 18O stable isotope labeling strategy.

RESULTS

We detected 16 previously unknown circulating fragments of proBNP peptides (9 of which are located in the N-terminal and 7 in the C-terminal region), revealing a more advanced state of degradation than previously known. Two of these fragments are indicative of either unidentified processing modes or a far-reaching C-terminal degradation (or a combination thereof) of the precursor proBNP.

CONCLUSIONS

Our results further restrict ideal target epitopes for immunoassay antibodies and expand the current thinking of diversity, degradation, and processing of proBNP, as well as the distribution of circulating forms.

Clinical Efficacy and Safety of Qishen Yiqi Dropping Pill Combined with Conventional Western Medicine in the Treatment of Chronic Heart Failure: A Systematic Review and Meta-Analysis

Objective

The systematic review was designed to evaluate the safety and efficacy of Qishen Yiqi dropping pill combined with conventional Western medicine in the treatment of chronic heart failure (CHF).

Methods

Relevant randomized controlled trials (RCTs) investigating the clinical efficacy of Qishen Yiqi dropping pill combined with conventional Western medicine in treating CHF were widely searched in electronic databases, including PubMed, Cochrane Library, EMBASE, CBM, CNKI, Read-show database, VIP database, and WanFang up to December 26, 2020. The methodological quality of each trial was assessed according to the Cochrane Reviewers' Handbook 5.0. Meta-analysis was performed by using Review Manager 5.3.

Results

Twenty-one RCTs (N = 2162) that met the criteria were included in the review for the assessment of methodological quality. Meta-analysis showed that compared with the conventional Western medicine (control group), Qishen Yiqi dropping pill combined with conventional Western medicine (experience group) significantly improved clinical efficiency, left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricular ejection fraction (LVEF), brain natriuretic peptide level (BNP), 6 min-walk distance (6-MWD), and adverse reactions.

Conclusion

Qishen Yiqi dropping pill combined with conventional Western medicine are better than conventional Western medicine alone to improve the indicators of patients with CHF, which provides a certain basis for the treatment of CHF.

Robust and sensitive peptidomics workflow for plasma based on specific extraction, lipid removal, capillary LC setup and multinozzle ESI emitter

We present a new workflow for the LC-MS determination of native peptides in plasma at picomolar levels. Collected whole blood was quickly diluted with an ice-cold solution in order to stop protease activity. Diluted plasma samples were extracted by protein denaturation followed by solid-phase-extraction with a polymeric stationary phase that removed most proteins and lipids. Using a specific LC-MS setup with 3 pumps, 240 μL of extracts were injected without drying-reconstitution, a step known to cause peptide losses. After an 18-fold dilution on-line, peptides were trapped on a 1 × 10 mm C8 column, back-flushed and resolved on a 0.3 × 100 mm C18 column. Extract reproducibility, robustness (column clogging), extraction yields, matrix effects, calibration curves and limits of detection were evaluated with plasma extracts and spiked-in standards. The sensitivity and applicability of 3 electrospray sources were evaluated at capillary flow rates (10 μL/min). We show that ionization sources must have a spray angle with the MS orifice when "real" extracts are injected and that a multinozzle emitter can improve very significantly peptide detection. Finally, using our workflow, we have performed a peptidomics study on dried-blood-spots collected over 65 h in a healthy volunteer and discovered 5 fragments (2.9-3.8 KDa) of the protein statherin showing circadian oscillations. This is the first time that statherin is observed in blood where its role clearly deserves further investigations. Our peptidomic protocol shows low picomolar limits of detection and can be readily applied with or without minor modifications for most peptide determinations in various biomatrices.

Recent advances in cardiac biomarkers detection: From commercial devices to emerging technologies

Although cardiac pathologies are the major cause of death in the world, it remains difficult to provide a reliable diagnosis to prevent heart attacks. Rapid patient care and management in emergencies are critical to prevent dramatic consequences. Thus, relevant biomarkers such as cardiac troponin and natriuretic peptides are currently targeted by commercialized Point-Of-Care immunoassays. Key points still to be addressed concern cost, lack of standardization, and poor specificity, which could limit the reliability of the assays. Consequently, alternatives are emerging to address these issues. New probe molecules such as aptamers or molecularly imprinted polymers should allow a reduction in cost of the assays and an increase in reproducibility. In addition, the assay specificity and reliability could be improved by enabling multiplexing through the detection of several molecular targets in a single device.

Normative Values of High-Sensitivity Cardiac Troponin T and N-Terminal pro-B-Type Natriuretic Peptide in Children and Adolescents: A Study from the CALIPER Cohort

BACKGROUND

Cardiac troponin (cTn) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) are increasingly used clinically to evaluate and prognosticate acute myocardial infarction and heart failure, respectively. Pediatric reference intervals and cut-offs have not been established for Roche's Elecsys Troponin T hs (high sensitive) assay. Although pediatric reference intervals exist for NT-proBNP, cut-off values do not exist. In this study, we report reference intervals and 99th percentile cut-offs in a large, healthy Canadian pediatric population using the CALIPER cohort.

METHODS

Blood samples from 484 healthy children and adolescents between 0 and <19 years old were recruited from hospital outpatient clinics and community settings. Serum samples were analyzed using Roche's Cobas e411 and evaluated for high-sensitivity cTnT (hs-cTnT) and NT-proBNP concentrations. 95% reference intervals and 99th percentile cut-off values were established.

RESULTS

Three hs-cTnT age partitions were established (0 to <6 months, 6 months to <1 year, and 1 to <19 years) with highest concentrations observed in children under 1 year. Two NT-proBNP age partitions were established (0 to <1 year, and 1 to <19 years), also with higher concentrations in infants under 1 year of age. For each of these age partitions, the 99th percentile cut-off, 95% reference interval, and proportion of detectable concentrations were determined.

CONCLUSIONS

This is the first study to examine hs-cTnT and NT-proBNP reference values together in a healthy pediatric cohort without other clinical indications. We present 99th percentile cut-offs, which will allow clinicians to appropriately evaluate cardiovascular disease in children and adolescents.

An atlas of O-linked glycosylation on peptide hormones reveals diverse biological roles

Peptide hormones and neuropeptides encompass a large class of bioactive peptides that regulate physiological processes like anxiety, blood glucose, appetite, inflammation and blood pressure. Here, we execute a focused discovery strategy to provide an extensive map of O-glycans on peptide hormones. We find that almost one third of the 279 classified peptide hormones carry O-glycans. Many of the identified O-glycosites are conserved and are predicted to serve roles in proprotein processing, receptor interaction, biodistribution and biostability. We demonstrate that O-glycans positioned within the receptor binding motifs of members of the neuropeptide Y and glucagon families modulate receptor activation properties and substantially extend peptide half-lives. Our study highlights the importance of O-glycosylation in the biology of peptide hormones, and our map of O-glycosites in this large class of biomolecules serves as a discovery platform for an important class of molecules with potential opportunities for drug designs.

Analysis of B-type natriuretic peptide impurities using label-free data-independent acquisition mass spectrometry technology

Objectives

Synthetic B-type natriuretic peptide (BNP) is employed in most clinical testing platforms as a raw material of calibrator. Characterization of impurities with structures similar (BNPstrimp compounds) to that of BNP is a reasonable way to decrease clinical measurement errors and improve drug safety.

Methods

A novel quantitative method targeted towards BNPstrimp compounds was developed. First, the peptide samples were separated and identified using ultra-performance liquid chromatography, coupled with high-resolution mass spectrometry (MS). To evaluate biological activity further, BNPstrimp immunoaffinity was investigated using western blot (WB) assays. Second, a quantitative label-free data-independent acquisition (DIA) MS approach was developed, and the internal standard peptide (ISP) was hydrolyzed. Absolute quantification was performed using an isotope dilution MS (ID-MS) approach. Third, method precision was investigated using the C-peptide reference material.

Results

Seventeen BNPstrimp compounds were identified in synthetic BNP, and 10 of them were successfully sequenced. The immunoassay results indicated that deaminated, oxidized, and isomerized BNPstrimp compounds exhibited weaker immunoaffinity than intact BNP1-32. The mass fraction of the synthetic solid ISP1-16, quantified by ID-MS, was 853.5 (±17.8) mg/g. Validation results indicated that the developed method was effective and accurate for the quantitation of the well-separated BNP impurities.

Conclusions

The developed approach was easy to perform, and it was suitable for the parallel quantification of low-abundance BNPstrimp compounds when they performed a good separation in liquid chromatography. The quantitative results were comparable and traceable. This approach is a promising tool for BNP product quality and safety assessment.

Cardiac natriuretic peptides

Investigations into the mixed muscle-secretory phenotype of cardiomyocytes from the atrial appendages of the heart led to the discovery that these cells produce, in a regulated manner, two polypeptide hormones - the natriuretic peptides - referred to as atrial natriuretic factor or atrial natriuretic peptide (ANP) and brain or B-type natriuretic peptide (BNP), thereby demonstrating an endocrine function for the heart. Studies on the gene encoding ANP (NPPA) initiated the field of modern research into gene regulation in the cardiovascular system. Additionally, ANP and BNP were found to be the natural ligands for cell membrane-bound guanylyl cyclase receptors that mediate the effects of natriuretic peptides through the generation of intracellular cGMP, which interacts with specific enzymes and ion channels. Natriuretic peptides have many physiological actions and participate in numerous pathophysiological processes. Important clinical entities associated with natriuretic peptide research include heart failure, obesity and systemic hypertension. Plasma levels of natriuretic peptides have proven to be powerful diagnostic and prognostic biomarkers of heart disease. Development of pharmacological agents that are based on natriuretic peptides is an area of active research, with vast potential benefits for the treatment of cardiovascular disease.

Atrial Tissue Pro-Fibrotic M2 Macrophage Marker CD163+, Gene Expression of Procollagen and B-Type Natriuretic Peptide

Background

Atrial tissue fibrosis is linked to inflammatory cells, yet is incompletely understood. A growing body of literature associates peripheral blood levels of the antifibrotic hormone BNP (B‐type natriuretic peptide) with atrial fibrillation (AF). We investigated the relationship between pro‐fibrotic tissue M2 macrophage marker Cluster of Differentiation (CD)163+, atrial procollagen expression, and BNP gene expression in patients with and without AF.

Methods and Results

In a cross‐sectional study design, right atrial tissue was procured from 37 consecutive, consenting, stable patients without heart failure or left ventricular systolic dysfunction, of whom 10 had AF and 27 were non‐AF controls. Samples were analyzed for BNP and fibro‐inflammatory gene expression, as well as fibrosis and CD163+. Primary analyses showed strong correlations (all P<0.008) between M2 macrophage CD163+ staining, procollagen gene expression, and myocardial BNP gene expression across the entire cohort. In secondary analyses without multiplicity adjustments, AF patients had greater left atrial volume index, more valve disease, higher serum BNP, and altered collagen turnover markers versus controls (all P<0.05). AF patients also showed higher atrial tissue M2 macrophage CD163+, collagen volume fraction, gene expression of procollagen 1 and 3, as well as reduced expression of the BNP clearance receptor NPRC (all P<0.05). Atrial procollagen 3 gene expression was correlated with fibrosis and BNP gene expression was correlated with serum BNP.

Conclusions

Elevated atrial tissue pro‐fibrotic M2 macrophage CD163+ is associated with increased myocardial gene expression of procollagen and anti‐fibrotic BNP and is higher in patients with AF. More work on modulation of BNP signaling for treatment and prevention of AF may be warranted.

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.

BNP/NT-proBNP in pulmonary arterial hypertension: time for point-of-care testing?

Despite the advent of new therapies and improved outcomes in patients with pulmonary arterial hypertension (PAH), it remains a life-shortening disease and the time to diagnosis remains unchanged. Strategies to improve outcomes are therefore currently focused on earlier diagnosis and a treatment approach aimed at moving patients with PAH into a category of low-risk of 1-year mortality. B-type natriuretic peptide (BNP; or brain natriuretic peptide) and N-terminal prohormone of BNP (NT-proBNP) are released from cardiac myocytes in response to mechanical load and wall stress. Elevated levels of BNP and NT-proBNP are incorporated into several PAH risk stratification tools and screening algorithms to aid diagnosis of systemic sclerosis. We have undertaken a systematic review of the literature with respect to the use of BNP and NT-proBNP in PAH and the use of these biomarkers in the diagnosis and risk stratification of PAH, their relation to pulmonary haemodynamics and the potential for point-of-care testing to improve diagnosis and prognosis.

True Chromogranin A concentrations in plasma from patients with small intestinal neuroendocrine tumours

Objective: The incidence of enteropancreatic neuroendocrine tumours (NET) is increasing. Chromogranin A (CgA) in plasma is a marker in patients suspected of NET tumours. CgA, however, is a precursor protein subjected to cellular processing that challenges quantitation and hence the use of CgA in diagnostics.Materials and methods: CgA concentrations in plasma sampled from 130 well-characterized patients with small intestinal NETs and from 30 healthy subjects were measured with eight commercial CgA kits, an in-house radioimmunoassay (RIA) and a processing-independent assay (PIA). For the evaluation of diagnostic accuracy, we performed regression analyses and plotted receiver-operating characteristic curves (ROC). The specificity was further assessed by size chromatography.Results: Five commercial assays (Thermo-Fisher, DRG Diagnostics, Eurodiagnostica (RIA and ELISA), and Phoenix), displayed a diagnostic accuracy with area under the curve (AUC) values >0.90, whereas three immunoassays (Yanaihara, CisBio RIA, and CisBio ELISA) discriminated poorly between disease stages (AUC: 0.60-0.78). Compared with the in-house assays, however, even the most accurate commercial immunoassay still missed patients with metastatic disease. Chromatography showed non-uniform patterns of large and small CgA fragments in plasma.Conclusion: Available commercial immunoassays measure CgA in plasma with gross variability. Three commercial CgA immunoassays discriminate so poorly between health and disease that they should not be used. The highest diagnostic accuracy was obtained with processing-independent measurement of total CgA concentrations in plasma.

Electrochemical Detection of NT-proBNP Using a Metalloimmunoassay on a Paper Electrode Platform

In this paper, we demonstrate an electrochemical method for detection of the heart failure biomarker, N-terminal prohormone brain natriuretic peptide (NT-proBNP). The approach is based on a paper electrode assembly and a metalloimmunoassay; it is intended for eventual integration into a home-use sensor. Sensing of NT-proBNP relies on the formation of a sandwich immunoassay and electrochemical quantification of silver nanoparticle (AgNP) labels attached to the detection antibodies (Abs). There are four important outcomes reported in this article. First, compared to physisorption of the detection Abs on the AgNP labels, a 27-fold increase in signal is observed when a heterobifunctional cross-linker is used to facilitate this labeling. Second, the assay is selective in that it does not cross-react with other cardiac natriuretic peptides. Third, the assay forms in undiluted human serum (though the electrochemical analysis is carried out in buffer). Finally, and most important, the assay is able to detect NT-proBNP at concentrations between 0.58 and 2.33 nM. This performance approaches the critical NT-proBNP concentration threshold often used by physicians for risk stratification purposes: ∼0.116 nM.

Natriuretic Peptides to Predict Short-Term Mortality in Patients With Sepsis: A Systematic Review and Meta-analysis

Data are conflicting regarding the optimal cutoffs of B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) to predict short-term mortality in patients with sepsis. We conducted a comprehensive search of several databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus) for English-language reports of studies evaluating adult patients with sepsis, severe sepsis, and septic shock with BNP/NT-proBNP levels and short-term mortality (intensive care unit, in-hospital, 28-day, or 30-day) published from January 1, 2000, to September 5, 2017. The average values in survivors and nonsurvivors were used to estimate the receiver operating characteristic curve (ROC) using a parametric regression model. Thirty-five observational studies (3508 patients) were included (median age, 51-75 years; 12%-74% males; cumulative mortality, 34.2%). A BNP of 622 pg/mL had the greatest discrimination for mortality (sensitivity, 0.695 [95% CI, 0.659-0.729]; specificity, 0.907 [95% CI, 0.810-1.003]; area under the ROC, 0.766 [95% CI, 0.734-0.797]). An NT-proBNP of 4000 pg/mL had the greatest discrimination for mortality (sensitivity, 0.728 [95% CI, 0.703-0.753]; specificity, 0.789 [95% CI, 0.710-0.867]; area under the ROC, 0.787 [95% CI, 0.766-0.809]). In prespecified subgroup analyses, identified BNP/NT-proBNP cutoffs had higher discrimination if specimens were obtained 24 hours or less after admission, in patients with severe sepsis/septic shock, in patients enrolled after 2010, and in studies performed in the United States and Europe. There was inconsistent adjustment for renal function. In this hypothesis-generating analysis, BNP and NT-proBNP cutoffs of 622 pg/mL and 4000 pg/mL optimally predicted short-term mortality in patients with sepsis. The applicability of these results is limited by the heterogeneity of included patient populations.

Prognostic value of NT-proBNP in patients with severe COVID-19

BACKGROUND

The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in China has been declared a public health emergency of international concern. The cardiac injury is a common condition among the hospitalized patients with COVID-19. However, whether N terminal pro B type natriuretic peptide (NT-proBNP) predicted outcome of severe COVID-19 patients was unknown.

METHODS

The study initially enrolled 102 patients with severe COVID-19 from a continuous sample. After screening out the ineligible cases, 54 patients were analyzed in this study. The primary outcome was in-hospital death defined as the case fatality rate. Research information and following-up data were obtained from their medical records.

RESULTS

The best cut-off value of NT-proBNP for predicting in-hospital death was 88.64 pg/mL with the sensitivity for 100% and the specificity for 66.67%. Patients with high NT-proBNP values (> 88.64 pg/mL) had a significantly increased risk of death during the days of following-up compared with those with low values (≤88.64 pg/mL). After adjustment for potential risk factors, NT-proBNP was independently correlated with in-hospital death.

CONCLUSION

NT-proBNP might be an independent risk factor for in-hospital death in patients with severe COVID-19.

TRIAL REGISTRATION

ClinicalTrials, NCT04292964. Registered 03 March 2020.

Association Between Cardiac Natriuretic Peptides and Lipid Profile: a Systematic Review and Meta-Analysis

Cardiac natriuretic peptides (NPs) play a fundamental role in maintaining cardiovascular (CV) and renal homeostasis. Moreover, they also affect glucose and lipid metabolism. We performed a systematic review and meta-analysis of studies investigating the association of NPs with serum lipid profile. A PubMed and Scopus search (2005–2018) revealed 48 studies reporting the association between NPs and components of lipid profile [total cholesterol (TC), low-density lipoprotein cholesterol (LDLc), high-density lipoprotein cholesterol (HDLc) and triglycerides (TG)]. Despite high inconsistency across studies, NPs levels were inversely associated with TC [k = 32; pooled r = −0.09; I² = 90.26%], LDLc [k = 31; pooled r = −0.09; I² = 82.38%] and TG [k = 46; pooled r = −0.11; I² = 94.14%], while they were directly associated with HDLc [k = 41; pooled r = 0.06; I² = 87.94%]. The relationship with LDLc, HDLc and TG lost significance if only studies on special populations (works including subjects with relevant acute or chronic conditions that could have significantly affected the circulating levels of NPs or lipid profile) or low-quality studies were taken into account. The present study highlights an association between higher NP levels and a favorable lipid profile. This confirms and extends our understanding of the metabolic properties of cardiac NPs and their potential in CV prevention.

Educational Recommendations on Selected Analytical and Clinical Aspects of Natriuretic Peptides with a Focus on Heart Failure: A Report from the IFCC Committee on Clinical Applications of Cardiac Bio-Markers

The IFCC Committee on Clinical Applications of Cardiac Bio-Markers (C-CB) has directives and initiatives focused on providing evidence-based educational resources to aid and improve understanding around key analytical and clinical aspects of cardiac biomarkers used in clinical practice and the research setting. As a task force, we have previously published position statements and recommendations focused on use and analytical aspects of high-sensitivity cardiac troponin assays. The current educational document is the first from the C-CB highlighting important biochemical, analytical, and clinical aspects as they relate to the natriuretic peptides (NPs), including B-type natriuretic peptide (BNP) and N-terminal pro–B-type natriuretic peptide (NT-proBNP), with a focus on heart failure.

How Do Contrast Agents Affect Cardiac Markers and Coagulation Tests? Experimental Study

Background:

The discovery that biotin interferes with results of troponin and Nt-proBNP led some commercial firms to update their measurement methods. In particular, the clinical incompatibility of cardiac test results may affect the risk of morbidity and mortality.

Objective:

The aim of this study is to investigate the interference effects of 7 different contrast agents on cardiac markers (Troponin-I, Nt-proBNP, Mass CK-MB, CK, AST, LDH) and in coagulation tests (PT, APTT).

Methods:

Seven different contrast media were added into control materials by using interference protocol. The concentrations of PT, APTT, CK, AST, LDH, Mass CK-MB, Troponin-I, and Nt-proBNP were measured by Sysmex CS-2100, Abbott c16000, Siemens Centaur XP and AFİAS-6 analyzer. The number of deviations from target values was calculated.

Results:

The 7 different contrast media caused negative interference in troponin levels between 57.43% and 62.87%. It was found that different contrast media produced false negativity in the Nt-proBNP test, ranging from 6.11% to 96.01%. Enzymes and coagulation tests were less affected.

Conclusion:

Different contrast media may cause false negatives in cTnI and Nt-proBNP. The contrast medium that causes the least interference should be preferred. The results of samples taken in the first hour after contrast imaging should be interpreted with care.

ProBNP That Is Not Glycosylated at Threonine 71 Is Decreased with Obesity in Patients with Heart Failure

BACKGROUND

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Plasma concentrations of B-type natriuretic peptide (BNP) or its amino terminal congener (NT-proBNP) are used for HF diagnosis and risk stratification. Because BNP concentrations are inexplicably lowered in obese patients, we investigated the relationship between proBNP glycosylation, plasma NT-proBNP, and body mass index (BMI) in HF patients.

METHODS

Three assays were developed to distinguish between total proBNP (glycosylated plus nonglycosylated proBNP), proBNP not glycosylated at threonine 71 (NG-T71), and proBNP not glycosylated in the central region (NG-C). Intraassay and interassay CVs were <15%; limits of detection were <21 ng/L; and samples diluted in parallel.

RESULT

Applying these assays and an NT-proBNP assay to plasma samples from 106 healthy volunteers and 238 HF patients determined that concentrations [median (interquartile range)] of proBNP, NG-T71, and NT-proBNP were greater in HF patients compared with controls [300 (44-664), 114 (18-254), and 179 (880-3459) ng/L vs 36 (18-229), 36 (18-175), and 40 (17-68) ng/L, respectively; all P < 0.012]. NG-C was undetectable in most samples. ProBNP concentrations in HF patients with BMI more or less than 30 kg/m² were not different (P = 0.85), whereas HF patients with BMI >30 kg/m² had lower NT-proBNP and NG-T71 concentrations (P < 0.003) and higher proBNP/NT-proBNP and proBNP/NG-T71 ratios (P = 0.001 and P = 0.02, respectively) than those with BMI <30 kg/m².

CONCLUSIONS

Increased BMI is associated with decreased concentrations of proBNP not glycosylated at T71. Decreased proBNP substrate amenable to processing could partially explain the lower NT-proBNP and BNP concentrations observed in obese individuals, including those presenting with HF.

Harmonization of Liquid Chromatography-Tandem Mass Spectrometry Protein Assays

Harmonization of diagnostic test results is fundamental to the effective use of laboratory testing in the diagnosis, treatment, and monitoring of disease. Formal approaches to harmonization and standardization provide a rigorous and high-quality roadmap to this end, although the formal harmonization process can be long and complex. In the meantime, more informal approaches to harmonization can provide a useful pathway to improved harmonization in the short term. Factors relevant to harmonization are discussed with particular attention to protein assays using LC-MS/MS. Published formal and informal harmonization projects are provided as examples, including lessons drawn from these projects.

Analytical barriers in clinical B-type natriuretic peptide measurement and the promising analytical methods based on mass spectrometry technology

B-type natriuretic peptide (BNP) is a circulating biomarker that is mainly applied in heart failure (HF) diagnosis and to monitor disease progression. Because some identical amino acid sequences occur in the precursor and metabolites of BNP, undesirable cross-reactions are common in immunoassays. This review first summarizes current analytical methods, such as immunoassay- and mass spectrometry (MS)-based approaches, including the accuracy of measurement and the inconsistency of the results. Second, the review presents some promising approaches to resolve the current barriers in clinical BNP measurement, such as how to decrease cross-reactions and increase the measurement consistency. Specific approaches include research on novel BNP assays with higher-specificity chemical antibodies, the development of International System of Units (SI)-traceable reference materials, and the development of structure characterization methods based on state-of-the-art ambient and ion mobility MS technologies. The factors that could affect MS analysis are also discussed, such as biological sample cleanup and peptide ionization efficiency. The purpose of this review is to explore and identify the main problems in BNP clinical measurement and to present three types of approaches to resolve these problems, namely, materials, methods and instruments. Although novel approaches are proposed here, in practice, it is worth noting that the BNP-related peptides including unprocessed proBNP were all measured in clinical BNP assays. Therefore, approaches that aimed to measure a specific BNP or proBNP might be an effective way for the standardization of a particular BNP form measurement, instead of the standardization of “total” immunoreactive BNP assays in clinical at present.

Reduced graphene oxide biosensor platform for the detection of NT-proBNP biomarker in its clinical range

Reduced graphene oxide (rGO) thin films can be exploited as highly sensitive transducer layers and integrated in interdigital micro-electrode systems for biosensing processes. The distinctive bipolar characterisitics of rGO thin films can be modulated by a very low external electric field due to the electrostatic charges of biomolecules. These charges lead to a fast response in the readout signals of rGO based ion sensitive field-effect transistors (ISFETs). The characterisitc changes of rGO ISFETs enable a fast, accurate and reproducible detection of biomolecules. The biosensing mechanism offers a fast and label-free approach for analyte detection in contrast to the classical ELISA method. In this contribution, we introduce a reproducible fabrication process of rGO based field-effect transistors on wafer level. The sensors are functionalized as biosensors to measure N-terminal pro-brain natriuretic peptide (NT-proBNP) in human serum within its clinical range. Our optimized rGO sensor shows very promising electrical properties and can be considered as a proof of concept study for the detection of various analytes. The easy and cost-effective fabrication as well as the versatile usability make this new technological platform an auspicious tool for different sensing applications in future.

Electrochemical Aptamer-Based Biosensors for the Detection of Cardiac Biomarkers

Rapid and accurate diagnostic technologies for early-state identification of cardiovascular abnormalities have become of high importance to prevent and attenuate their progression. The capability of biosensors to determine an increase in the concentration of cardiovascular protein biomarkers in circulating blood immediately after a myocardial infarction makes them ideal point-of-care platforms and alternative approaches to electrocardiograms, chest X-rays, and different laboratory-based immunoassays. We report here a generic approach toward multianalyte sensing platforms for cardiac biomarkers by developing aptamer-based electrochemical sensors for brain natriuretic peptide (BNP-32) and cardiac troponin I (cTnI). For this, commercial gold-based screen-printed electrodes were modified electrophoretically with polyethyleneimine/reduced graphene oxide films. Covalent grafting of propargylacetic acid integrates propargyl groups onto the electrode to which azide-terminated aptamers can be immobilized using Cu(I)-based "click" chemistry. To ensure low biofouling and high specificity, cardiac sensors were modified with pyrene anchors carrying poly(ethylene glycol) units. In the case of BNP-32, the sensor developed has a linear response from 1 pg mL^-1 to 1 μg mL^-1 in serum; for cTnI, linearity is observed from 1 pg mL^-1 to 10 ng mL^-1 as demanded for early-stage diagnosis of heart failure. These electrochemical aptasensors represent a step further toward multianalyte sensing of cardiac biomarkers.

Natriuretic peptide family as diagnostic/prognostic biomarker and treatment modality in management of adult and geriatric patients with heart failure: remaining issues and challenges

B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP), the key members of natriuretic peptide family have been recommended as the gold standard biomarkers for the diagnosis and prognosis of heart failure (HF) according to the current clinical guidelines. However, recent studies have revealed many previously unrecognized features about the natriuretic peptide family, including more accurate utilization of BNP and NT-proBNP in diagnosing HF. The pathophysiological mechanisms behind natriuretic peptide release, breakdown, and clearance are very complex and the diverse nature of circulating natriuretic peptides and fragments makes analytical detection particularly challenging. In addition, a new class of drug therapy, which works via natriuretic peptide family, has also been considered promising for cardiology application. Under this context, our present mini-review aims at providing a critical analysis on these new progresses on BNP and NT-proBNP with a special emphasis on their use in geriatric cardiology settings. We have focused on several remaining issues and challenges regarding the clinical utilization of BNP and NT-proBNP, which include: (1) Different prevalence and diagnostic/prognostic values of BNP isoforms; (2) methodological issues on detection of BNP; (3) glycosylation of proBNP and its effect on biomarker testing; (4) specificity and comparability of BNP/NT-proBNP resulted from different testing platforms; (5) new development of natriuretic peptides as HF treatment modality; (6) BNP paradox in HF; and (7) special considerations of using BNP/NT-proBNP in elderly HF patients. These practical discussions on BNP/NT-proBNP may be instrumental for the healthcare providers in critically interpreting laboratory results and effective management of the HF patients.

Amniotic Fluid Natriuretic Peptide Levels in Fetuses With Congenital Heart Defects or Arrhythmias

BACKGROUND

We have previously demonstrated that umbilical cord plasma natriuretic peptide (NP) levels reflect the severity of heart failure (HF) in fetuses with congenital heart defects (CHD). The aim of this study was to evaluate the significance of amniotic fluid (AF) NP levels in the assessment of HF in fetuses with CHD or arrhythmia. Methods and Results: This was a prospective observational study at a tertiary pediatric cardiac center. A total of 95 singletons with CHD or arrhythmia, and 96 controls from 2012 to 2015 were analyzed. AF concentrations of atrial NP (ANP), B-type NP (BNP) and N-terminal pro-B-type NP (NT-proBNP) at birth were compared with ultrasonographic assessment of fetal HF using the cardiovascular profile (CVP) score. Multivariate analysis showed that a CVP score ≤5 and preterm birth are independently associated with high AF NT-proBNP levels. AF NT-proBNP levels of fetuses with CHD or arrhythmia inversely correlated with CVP score (P for trend <0.01). In contrast, AF concentrations of ANP and BNP were extremely low, and it was difficult to assess the degree of fetal HF based on them.

CONCLUSIONS

AF NT-proBNP concentrations increase in stepwise fashion with the severity of HF in fetuses with CHD or arrhythmia; it was the optimal NP for assessing the fetal HF.

Diagnostic concordance between NT-proBNP and BNP for suspected heart failure

OBJECTIVES

BNP and NT-proBNP are viewed as comparable in their ability to diagnose and monitor HF in clinical guidelines. However, no recent large-scale study has directly established diagnostic concordance between BNP and NT-proBNP. This study sought to assess diagnostic concordance of BNP and NT-proBNP for ruling in and ruling out heart failure (HF).

METHODS

Simultaneous BNP and NT-proBNP testing was performed on 2729 patient samples with routinely ordered BNP testing. Hospital location, age, sex, creatinine, BNP and NT-proBNP were also recorded. Recommended cutoffs for BNP and NT-proBNP for ruling in and out HF were used for assessing diagnostic concordance and correlation.

RESULTS

In the ED setting, concordance between BNP and NT-proBNP was 0.695 (95% CI, 0.668-0.723) by weighted kappa using the recommended cutoffs for the acute setting. In non-ED patients, the concordance was 0.642 (95% CI, 0.580-0.705) using non-acute setting cutoffs. In the ED setting, patients with eGFR <60 mL/min/1.73m² had lower overall concordance (0.626; 95% CI 0.580-0.672) compared to those with eGFR >60 mL/min/1.73m² (0.707, 95% CI 0.669-0.744). Patients with an eGFR <15 mL/min/1.73m² had a much higher ratio of NT-proBNP to BNP than patients with eGFR >60 mL/min/1.73m² (17.0 vs. 4.7, P < .001). Linear regression revealed an r² of 0.52 in the ED setting and 0.49 in the non-ED setting between BNP and NT-proBNP. For 368 patients with multiple measurements of natriuretic peptides, 19.7% of paired temporal measurements had an increase in one peptide and a decrease in the other.

CONCLUSION

The current cutoffs for diagnosing HF for NT-proBNP and BNP have relatively low diagnostic concordance and correlation, particularly among patients with chronic kidney disease.

One-pot synthesis of poly (acrylic acid)-stabilized Fe3O4 nanocrystal clusters for the simultaneously qualitative and quantitative detection of biomarkers in lateral flow immunoassay

Lateral flow immunoassay (LFIAs) has found widespread applications in point-of-care testing (POCT). However, conventional LFIAs based on gold nanoparticles can only provide limited information (qualitative or semi-quantitative information) and suffer from low sensitivity. To address this issue, we developed a Fe₃O₄ nanocrystal cluster-based highly sensitive LFIAs for the simultaneously qualitative and quantitative detection of trace-level biomarkers. The synthesis of poly (acrylic acid)-stabilized superparamagnetic nanocrystal clusters (PAA-MNCs) is a one-pot, simple and convenient technique, and the polyelectrolyte coating provides enough stability, good dispersity and downstream conjugation sites. Using these PAA-MNCs as a label nanomaterial in LFIAs, a model biomarker (amino-terminal pro-B-type natriuretic peptide (NT-proBNP) antibody) was detected qualitatively and quantitatively. The results show that tests have a qualitative detection limit of 100 pg/mL and a quantitative linear relationship between the magnetic signal and antibody concentration (20-8000 pg/mL) under the optimized experimental conditions. The developed LFIA based on PAA-MNCs for NT-proBNP could be used for the clinical assessment of heart failure, offering tremendous potential for personalized medicine.

Brain Natriuretic Peptide and Its Biochemical, Analytical, and Clinical Issues in Heart Failure: A Narrative Review

Heart failure (HF) is a primary cause of morbidity and mortality worldwide. As the most widely studied and commonly applied natriuretic peptide (NP), B-type natriuretic peptide (BNP) has the effects of diuresis, natriuresis, vasodilation, anti-hypertrophy, and anti-fibrosis and it inhibits the renin-angiotensin-aldosterone and sympathetic nervous systems to maintain cardiorenal homeostasis and counteract the effects of HF. Both BNP and N-terminal pro B-type natriuretic peptide (NT-proBNP) are applied as diagnostic, managing, and prognostic tools for HF. However, due to the complexity of BNP system, the diversity of BNP forms and the heterogeneity of HF status, there are biochemical, analytical, and clinical issues on BNP not fully understood. Current immunoassays cross-react to varying degrees with pro B-type natriuretic peptide (proBNP), NT-proBNP and various BNP forms and cannot effectively differentiate between these forms. Moreover, current immunoassays have different results and may not accurately reflect cardiac function. It is essential to design assays that can recognize specific forms of BNP, NT-proBNP, and proBNP to obtain more clinical information. Not only the processing of proBNP (corin/furin) and BNP (neprilysin), but also the effects of glycosylation on proBNP processing and BNP assays, should be targeted in future studies to enhance their diagnostic, therapeutic, and prognostic values.

Standardization of BNP and NT-proBNP Immunoassays in Light of the Diverse and Complex Nature of Circulating BNP-Related Peptides

Brain natriuretic peptide (BNP) and the N-terminal fragment of the BNP precursor (NT-proBNP) are widely used as heart failure (HF) biomarkers. Since the discovery of BNP in 1988, much effort has been allocated to the precise detection of BNP and NT-proBNP levels for reliable HF diagnostics. As a result, measurements of these biomarkers are globally accepted and used in clinical practice for the diagnosis of acute and chronic HF, risk stratification, and monitoring response to therapy. Several immunoassays specific for BNP and NT-proBNP are currently commercially available. Recent comparative studies show that there are marked differences between different BNP and NT-proBNP assays and platforms, and the results of measurements are not comparable enough. The lack of equivalence between the assays complicates the interpretation of the results and renders the cut-off points for diagnostic decisions to be method dependent. Presently, there is no agreement on what kind of BNP or NT-proBNP standard should be used for calibration, and a certified reference material as well as reference measurement procedures are lacking. The aim of this chapter is to summarize the available data on the complex nature of BNP-related peptides, specificity for existing BNP and NT-proBNP immunoassays, and to discuss potential approaches for standardization of BNP and NT-proBNP measurements.

Sex-Related Aspects of Biomarkers in Cardiac Disease

Biomarkers play an important role in the clinical management of cardiac care. In particular, cardiac troponins (cTn) and natriuretic peptides are the cornerstones for the diagnosis of acute myocardial infarction (AMI) and for the diagnosis of heart failure (HF), respectively. Current guidelines do not make a distinction between women and men. However, the commonly used "one size fits all" algorithms are topic of debate to improve assessment of prognosis, particularly in women. Due to the high-sensitivity assays (hs-cTn), lower cTn levels (and 99th percentile upper reference limits) were observed in women as compared with men. Sex-specific diagnostic thresholds may improve the diagnosis of AMI in women, though clinical relevance remains controversial and more trials are needed. Also other diagnostic aspects are under investigation, like combined biomarkers approach and rapid measurement strategies. For the natriuretic peptides, previous studies observed higher concentrations in women than in men, especially in premenopausal women who might benefit from the cardioprotective actions. Contrary to hs-cTn, natriuretic peptides are particularly incorporated in the ruling-out algorithms for the diagnosis of HF and not ruling-in. Clinical relevance of sex differences here seems marginal, as clinical research has shown that negative predictive values for ruling-out HF were hardly effected when applying a universal diagnostic threshold that is independent from sex or other risk factors. Apart from the diagnostic issues of AMI in women, we believe that in the future most sex-specific benefits of cardiac biomarkers can be obtained in patient follow-up (guiding therapy) and prognostic applications, fitting modern ideas on preventive and personalized medicine.

New issues on measurement of B-type natriuretic peptides

The measurement of the active hormone of B-type natriuretic peptide (BNP) system actually has several analytical limitations and difficulties in clinical interpretations compared to that of inactive peptide N-terminal proBNP (NT-proBNP) because of the different biochemical and pathophysiological characteristics of two peptides and quality specifications of commercial immunoassay methods used for their measurement. Because of the better analytical characteristics of NT-proBNP immunoassays and the easier pathophysiological and clinical interpretations of variations of NT-proBNP levels in patients with heart failure (HF), some authors claimed to measure the inactive peptide NT-proBNP instead of the active hormone BNP for management of HF patients. The measurement of the active peptide hormone BNP gives different, but complementary, pathophysiological and clinical information compared to inactive NT-proBNP. In particular, the setup of new more sensitive and specific assays for the biologically active peptide BNP1-32 should give better accurate information on circulating natriuretic activity. In conclusion, at present time, clinicians should accurately consider both the clinical setting of patients and the analytical characteristics of BNP and NT-proBNP immunoassays in order to correctly interpret the variations of natriuretic peptides measured by commercially available laboratory methods, especially in patients treated with the new drug class of angiotensin receptor-neprilysin inhibitors.