Amino-terminal pro-B-type natriuretic peptide: analytic considerations

Sendaway capillary NT-proBNP in pulmonary hypertension

BACKGROUND

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a biomarker of cardiac ventricular wall stress that is incorporated into pulmonary hypertension (PH) risk stratification models. Sendaway sampling may enable patients to perform NT-proBNP tests remotely. This UK-wide study aimed to assess the agreement of sendaway NT-proBNP with standard venous NT-proBNP and to assess the effect of delayed processing.

METHODS

Reference venous NT-proBNP was collected from PH patients. Samples for capillary and venous sendaway tests were collected contemporaneously, mailed to a reference laboratory and processed at 3 and 7 days using a Roche Cobas e411 device. Differences in paired measurements were analysed with Passing-Bablok regression, percentage difference plots and the % difference in risk strata.

RESULTS

113 patients were included in the study. 13% of day 3 capillary samples were insufficient. Day 3 capillary samples were not equivalent to reference samples (Passing Bablok analysis slope of 0.91 (95% CI 0.88 to 0.93) and intercept of 6.0 (95% CI 0.2 to 15.9)). The relative median difference was -7% and there were acceptable limits of agreement. Day 3 capillary NT-proBNP accurately risk stratified patients in 93.5% of cases. By comparison, day 3 venous results accurately risk stratified patients in 90.1% of cases and were equivalent by Passing-Bablok regression. Delayed sampling of sendaway tests led to an unacceptable level of agreement and systematically underestimated NT-proBNP.

CONCLUSIONS

Sendaway NT-proBNP sampling may provide an objective measure of right ventricular strain for virtual PH clinics. Results must be interpreted with caution in cases of delayed sampling.

Associations between diet quality and NT-proBNP in U.S. adults, NHANES 1999-2004

Objective

N-terminal pro-brain-type natriuretic peptide (NT-proBNP) is a marker of cardiac wall stress and is a predictor of cardiovascular disease. Higher diet quality is associated with lower risk of cardiovascular disease. The association between diet quality and subclinical cardiovascular disease assessed by NT-proBNP is uncharacterized. We investigated the associations between diet quality, using Healthy Eating Index-2015 (HEI-2015), and NT-proBNP from the National Health and Nutrition Examination Survey (NHANES) 1999-2004.

Methods

We included 9,782 adults from NHANES 1999-2004 without self-reported cardiovascular disease. The HEI-2015 ranges from 0 to 100, with higher scores indicating better diet quality. The HEI-2015 was categorized into sex-specific quintiles. Regression models were used to quantify associations between the overall HEI-2015 score and its 13 components with log-transformed NT-proBNP. The beta coefficients were converted to percent differences.

Results

Among 9,782 participants, mean age was 45 years, 48% were men, and 72% were non-Hispanic White adults. After adjusting for sociodemographic characteristics, lifestyle factors, and medical history, those in the highest vs. lowest HEI-2015 quintile had an 8.5% (95% CI: -14.6% to -2.0%) lower NT-proBNP level. There was a dose-response association between HEI-2015 and NT-proBNP (P value for trend = 0.01). Each 1-unit higher in sodium and added sugars score indicating lower intake was associated with lower NT-proBNP by 7.7% (95% CI: -12.8% to -2.2%) and 6.5% (95% CI: -12.0% to -0.7%), respectively.

Conclusion

Higher diet quality, especially lower intakes of sodium and added sugars, was associated with lower serum levels of NT-proBNP.

NT-proBNP and All-Cause and Cardiovascular Mortality in US Adults: A Prospective Cohort Study

Background NT-proBNP (N-terminal pro-B-type natriuretic peptide) is strongly associated with mortality in patients with heart failure. Prior studies, primarily in middle-aged and older populations, have suggested that NT-proBNP has prognostic value in ambulatory adults. Methods and Results We conducted a prospective cohort analysis of adults, aged ≥20 years, in the nationally representative 1999 to 2004 National Health and Nutrition Examination Survey, to characterize the association of NT-proBNP with mortality in the general US adult population overall and by age, race and ethnicity, and body mass index. We used Cox regression to characterize associations of NT-proBNP with all-cause and cardiovascular disease (CVD) mortality through 2019, adjusting for demographics and cardiovascular risk factors. We included 10 645 individuals (mean age, 45.7 years; 50.8% women; 72.8% White adults; 8.5% with a self-reported history of CVD). There were 3155 deaths (1009 CVD-related) over a median 17.3 years of follow-up. Among individuals without prior CVD, elevated NT-proBNP (≥75th percentile [81.5 pg/mL] versus <25th percentile [20.5 pg/mL]) was associated with a significantly higher risk of all-cause (hazard ratio [HR], 1.67 [95% CI, 1.39-2.00]) and CVD mortality (HR, 2.87 [95% CI, 1.61-5.11]). Associations of NT-proBNP with all-cause and CVD mortality were generally similar across subgroups defined by age, sex, race and ethnicity, or body mass index (all P interaction >0.05). Conclusions In a representative sample of the US adult population, NT-proBNP was an important independent risk factor for all-cause and CVD mortality. NT-proBNP may be useful for monitoring risk in the general adult population.

Performance of the Abbott Architect Immuno-Chemiluminometric NT-proBNP Assay

Background: We evaluated the performance of the Abbott N-terminal pro-brain natriuretic peptide (NT-proBNP) assay against the Roche NT-proBNP immunoassay across two sites. Methods: Precision, linearity, and sensitivity studies were performed. A combined method of comparison and regression analysis was performed between the Roche and Abbott assays using samples from both sites (n = 494). To verify biotin interference, lyophilised biotin powder was reconstituted and spiked into serum samples at two medical decision levels (final concentration 500/4250 ng/mL) and compared to controls. NT-proBNP was also measured in anonymised leftover sera (n = 388) in a cardio-renal healthy population and stratified into three age bands—<50 (n = 145), 50−75 (n = 183) and >75 (n = 60). Results: Between-run precision (CV%) for NT-proBNP was 4.17/4.50 (139.5/142.0 pg/mL), 3.83/2.17 (521.6/506.3), and 4.60/2.51 (5053/4973), respectively. The assay was linear from 0.7−41,501 pg/mL. The limit of blank/quantitation was 1.2/7.9 pg/mL. The assay showed no interference from biotin up to 4250 ng/mL. Passing−Bablok regression analysis showed excellent agreement between the two assays (r = 0.999, 95% CI 0.999 to 0.999, p < 0.0001). The Roche assay had a slightly persistent, negative bias across different levels of NT-proBNP. ESC age cut-offs for diagnosing acute heart failure are applicable for the Abbott assay, with the median NT-proBNP of subjects < 50 years old at 43.0 pg/mL (range 4.9−456 pg/mL), 50−75 years old at 95.1 pg/mL (range 10.5−1079 pg/mL), and >75 years old at 173.1 pg/mL (range 23.2−1948 pg/mL). Conclusions: The Abbott Architect NT-proBNP assay has good performance that agrees with the manufacturer’s specifications. ESC/AHA recommended NT-proBNP age groups for acute heart failure diagnosis are applicable to this assay.

Glycemic excursions and subclinical cardiac damage in adults with type 2 diabetes: Results from the ADVANCE Trial

We found that 1,5-anhydroglucitol-a marker of glucose excursions-was not independently associated with subclinical cardiac damage, nor with vascular outcomes, in the ADVANCE Trial. High-sensitivity cardiac troponin T and N-terminal pro-b-type natriuretic peptide provided better prognostic information regarding vascular risk in diabetes than 1,5-anhydroglucitol.

Diagnostic value of cardiac natriuretic peptide on pulmonary hypertension in systemic sclerosis: A systematic review and meta-analysis

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a major cause of morbidity and mortality in systemic sclerosis (SSc). Many risk factors and predictors of outcomes have been identified in these patients. B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) serum levels are often elevated in SSc patients with early PAH. We conducted this systematic review and meta-analysis to estimate the diagnostic value of BNP/NT-proBNP in systemic sclerosis secondary pulmonary arterial hypertension (SSc-PAH).

METHODS

A systematic search was performed through PubMed, Embase, and Cochrane Library databases up to January 30, 2021. Stata 16.0 (Stata Corp, College Station, TX) was used to conduct the meta-analysis.

RESULTS

A total of 9 studies involving 220 SSc-PAH patients and 259 non-SSc-PAH controls were included. The values of sensitivity and specificity using BNP and NT-ProBNP as diagnostic tools were pooled in the diagnostic meta-analysis. The overall performance of BNP/NT-ProBNP detection was: pooled sensitivity, 0.67 (95% CI: 0.52 to 0.79); pooled specificity, 0.84 (95% CI: 0.75 to 0.91); pooled positive likelihood ratio, 4.3 (95% CI: 3 to 6.1); and pooled negative likelihood ratio, 0.39 (95% CI: 0.28 to 0.55). The subgroup analysis showed similar results. Funnel plots indicate that there is no evidence for publication bias.

CONCLUSIONS

Our results revealed that NT-proBNP has certain diagnostic value for PAH due to its better specificity and moderate sensitivity, but its clinical application value remains suboptimal and can not be a stand-alone decision-making diagnostic tool of SSc-PAH.

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.

Clinical Impact of N-Terminal Prohormone of Brain Natriuretic Peptide on Patients Hospitalized with Community-Acquired Pneumonia

BACKGROUND

Risk stratification is important for the management of community-acquired pneumonia (CAP). The present study aimed to investigate the clinical impact of N-terminal prohormone of brain natriuretic peptide (NT-proBNP) on prognosis and to identify clinical characteristics associated with NT-proBNP elevation in CAP patients.

METHODS

This retrospective study included patients hospitalized for CAP at a tertiary referral center and who underwent measurement plasma NT-proBNP levels. Based on 30-day mortality, patients (n = 1,821) were divided into 2 groups, survivors (n = 150) and nonsurvivors (n = 1,671), and clinical and laboratory findings were compared.

RESULTS

In multivariate analysis, blood levels of NT-proBNP (>942.5 pg/mL), albumin (<3.3 g/dL), and troponin I (>0.018 ng/mL) independently predicted 30-day mortality. Of these blood biomarkers, NT-proBNP exhibited the highest C-statistic, followed by albumin. NT-proBNP level/CURB-65 score and NT-proBNP level/pneumonia severity index (PSI) class exhibited significantly higher C-statistics than CURB-65 score and PSI class alone, respectively. The 3-test combinations of CURB-65 score/NT-proBNP level/albumin level and PSI class/NT-proBNP level/albumin level exhibited significantly higher C-statistics than the 2-test combinations. NT-proBNP elevation was associated with increased age, heart disease and chronic kidney disease and NT-proBNP levels only weakly or moderately correlated with other blood biomarkers.

CONCLUSIONS

NT-proBNP level was a useful marker for the prediction of 30-day mortality in patients hospitalized with CAP, and provided additional prognostic value to PSI or CURB-65 alone.

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.

Change in NT-proBNP (N-Terminal Pro-B-Type Natriuretic Peptide) Level and Risk of Dementia in Multi-Ethnic Study of Atherosclerosis (MESA)

Cross-sectionally measured NT-proBNP (N-terminal pro-B-type natriuretic peptide) is related to incident dementia. However, data linking changes in NT-proBNP to risk of future dementia are lacking. We aimed to examine the association of change in NT-proBNP over 3.2 years with incident dementia. We included 4563 participants in MESA (Multi-Ethnic Study of Atherosclerosis) prospective cohort who were free of cardiovascular disease at enrollment, had NT-proBNP level measured at MESA exams 1 (baseline, 2000-2002) and 3 (2004-2005), and had no diagnosis of dementia before exam 3. The association of change in NT-proBNP level between MESA exams 1 through 3 and all-cause hospitalized dementia (by International Classification of Diseases, Ninth Revision, codes) after MESA exam 3 (2004-2005) through 2015 was assessed using competing-risks Cox proportional hazard regression analysis. During 45 522 person-years of follow-up, 223 dementia cases were documented. Increase in log-NT-proBNP from MESA exams 1 through 3 was positively associated with incidence of dementia (multivariable hazard ratio, 1.28 [95% CI, 1.001-1.64]; P=0.049). An increase of at least 25% in NT-proBNP level from MESA exam 1 through 3 was associated with a 55% (P=0.02) increase in the risk of dementia in multivariable analysis. Addition of temporal NT-proBNP change to a model including risk factors and baseline NT-proBNP improved the prediction of dementia (Harrell C statistic from 0.85 to 0.87, P=0.049). Increase in NT-proBNP is independently associated with future all-cause hospitalized dementia and offers a moderately better predictive performance for risk of dementia compared with risk factors and baseline NT-proBNP. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT00005487.

Do N-terminal pro-brain natriuretic peptide levels determine the prognosis of community acquired pneumonia?

OBJECTIVE

Pneumonia is a leading cause of mortality worldwide, especially in the elderly. The use of clinical risk scores to determine prognosis is complex and therefore leads to errors in clinical practice. Pneumonia can cause increases in the levels of cardiac biomarkers such as N-terminal pro-brain natriuretic peptide (NT-proBNP). The prognostic role of the NT-proBNP level in community acquired pneumonia (CAP) remains unclear. The aim of this study was to evaluate the prognostic role of the NT-proBNP level in patients with CAP, as well as its correlation with clinical risk scores.

METHODS

Consecutive inpatients with CAP were enrolled in the study. At hospital admission, venous blood samples were collected for the evaluation of NT-proBNP levels. The Pneumonia Severity Index (PSI) and the Confusion, Urea, Respiratory rate, Blood pressure, and age ≥ 65 years (CURB-65) score were calculated. The primary outcome of interest was all-cause mortality within the first 30 days after hospital admission, and a secondary outcome was ICU admission.

RESULTS

The NT-proBNP level was one of the best predictors of 30-day mortality, with an area under the curve (AUC) of 0.735 (95% CI: 0.642-0.828; p < 0.001), as was the PSI, which had an AUC of 0.739 (95% CI: 0.634-0.843; p < 0.001), whereas the CURB-65 had an AUC of only 0.659 (95% CI: 0.556-0.763; p = 0.006). The NT-proBNP cut-off level found to be the best predictor of ICU admission and 30-day mortality was 1,434.5 pg/mL.

CONCLUSIONS

The NT-proBNP level appears to be a good predictor of ICU admission and 30-day mortality among inpatients with CAP, with a predictive value for mortality comparable to that of the PSI and better than that of the CURB-65 score.

Visit-to-Visit B-Type Natriuretic Peptide Variability during the Previous Year Has Independent Prognostic Value in Patients with Stable Chronic Heart Failure

BACKGROUND

There is wide variability of visit-to-visit (V2V) B-type natriuretic peptide (BNP) in patients with chronic heart failure (CHF), even when they are stable. The prognostic significance of V2V-BNP variability has not been investigated. We aimed to test whether V2V-BNP variability during the stable period of CHF has prognostic value regardless of BNP level.

METHODS

In 278 stable outpatients (75 ± 10 years, 65% male) with CHF, we studied V2V-BNP variability, which was defined as the coefficient of variance of BNP values measured during 1 year before enrollment. All-cause death and rehospitalization due to HF were considered the primary endpoint.

RESULTS

The median V2V-BNP variability was 25.7% (IQR: 19.2-34.4%). During the follow-up period (median 3.2 years), 100 patients reached the endpoint and those with high V2V-BNP variability (≥25.7%) had a significantly higher rate of events (p = 0.001). CHF severity in terms of BNP level and MAGGIC risk score was not significantly different between those with high and low V2V-BNP variability. Multivariable analysis showed that high V2V-BNP variability was independently associated with increased event rates even after adjustment for other known prognostic predictors, including BNP (hazard ratio 1.90, p = 0.003), or for MAGGIC risk score and BNP (hazard ratio 1.72, p = 0.010). The hazard for the outcome consistently increased as V2V-BNP variability increased, with a marked increase up to about 30%.

CONCLUSIONS

Even in the stable phase of CHF, V2V-BNP variability was associated with worse long-term outcomes, independent of BNP level.

High-level production of N-terminal pro-brain natriuretic peptide, as a calibrant of heart failure diagnosis, in Escherichia coli

Heart failure (HF) is a coronary disease that affects people worldwide and has a high mortality rate. N-terminal pro-brain natriuretic peptide (NT-proBNP) has been proven to be a useful and accurate biomarker for diagnosing systolic HF. Here, we report a strategy for the high-level production of recombinant (r)NT-proBNP in Escherichia coli. An Fh8 tag with six histidines was fused to the N terminus of NT-proBNP along with the recognition site of tobacco etch virus (TEV) protease; the 6HFh8-NT-proBNP fusion peptide was expressed in flask cultures of E. coli in almost completely soluble form. The peptide was purified by HisTrap affinity chromatography, and the N-terminal tag was cleaved by TEV protease. After a second round of HisTrap affinity chromatography to remove the TEV protease and N-terminal tag, rNT-proBNP was isolated with high purity (≥ 98%) by carboxymethyl cation exchange chromatography. The final yield of purified rNT-proBNP (97.5 mg/l of bacterial culture; 3.25 mg/g of wet cell) was 55-fold higher than that reported in previous studies (0.5-1.75 mg/l of bacterial culture). Furthermore, the high cell density E. coli fed-batch culture enabled high-level production of rNT-proBNP in the order of grams per liter. The purified rNT-proBNP was detected by enzyme-linked immunosorbent assay and chemiluminescence enzyme immunoassay using commercial monoclonal antibodies recognizing different epitopes, showing a linear dose-response relationship in the range of tested concentrations (slope = 3.58 and r² = 0.995). These results demonstrate the efficiency of our process for mass producing (gram-to-liter level) rNT-proBNP with acceptable analytical performance.

Cardiovascular biomarkers in clinical studies of type 2 diabetes

When planning cardiovascular (CV) studies in type 2 diabetes (T2D), selection of CV biomarkers is a complex issue. Because the pathophysiology of CV disease (CVD) in T2D is multifactorial, ideally, the selected CV biomarkers should cover all aspects of the known pathophysiology of the disease. This will allow the researcher to distinguish between effects on different aspects of the pathophysiology. To this end, we discuss a host of biomarkers grouped according to their role in the pathogenesis of CVD, namely: (1) cardiac damage biomarkers; (2) inflammatory biomarkers; and (3) novel biomarkers (oxidative stress and endothelial dysfunction biomarkers). Within each category we present the best currently validated biomarkers, with special focus on the population of interest (people with T2D). For each individual biomarker, we discuss the physiological role, validation in the general population and in people with T2D, analytical methodology, modifying factors, effects of glucose-lowering drugs, and interpretation. This approach will provide clinical researchers with the information necessary for planning, conducting and interpreting results from clinical trials. Furthermore, a systematic approach to selection of CV biomarkers in T2D research will improve the quality of future research.

Pedal Edema as an Indicator of Early Heart Failure in the Community: Prevalence and Associations With Cardiac Structure/Function and Natriuretic Peptides (MESA [Multiethnic Study of Atherosclerosis])

BACKGROUND

The prevalence of pedal edema (PE) and its associations with abnormal cardiac structure/function, natriuretic peptides, and incident heart failure (HF) is unknown, especially in community-dwelling adults without a history of cardiovascular disease.

METHODS AND RESULTS

Out of 5004 MESA (Multiethnic Study of Atherosclerosis) participants who had cardiac magnetic resonance imaging, 4196 had complete data and were included in this analysis (3501 for the right ventricle analysis). Logistic regression and Cox proportional hazard analyses were used to assess the associations among self-reported PE, 2-pillow orthopnea, paroxysmal nocturnal dyspnea, left and right ventricular structure and function, natriuretic peptide levels, and incident HF. PE was present in 28% of the participants. PE was not associated with overt left or right ventricular systolic dysfunction (ejection fraction <50%). PE was associated with 2-pillow orthopnea (odds ratio 1.66; 95% confidence interval [CI], 1.30-2.12), paroxysmal nocturnal dyspnea (odds ratio 1.95; 95% CI, 1.55-2.44), and abnormal N-terminal pro-B-type natriuretic peptide levels (defined as >400 pg/mL; odds ratio 1.80; 95% CI, 1.21-2.68) in adjusted models. After a mean of 10.2 years of follow-up, 184/4196 (4.4%) participants had an adjudicated incident HF hospitalization. PE was associated with incident HF hospitalization in models adjusted for age, sex, and race (hazard ratio 1.44; 95% CI, 1.05-1.97). This association persisted after adding additional covariates, including comorbidities, baseline left ventricular ejection fraction, and antecedent myocardial infarction (hazard ratio 1.43; 95% CI, 1.02-1.99). The association of PE with incident HF was attenuated by further adjustment for N-terminal pro-B-type natriuretic peptide.

CONCLUSIONS

PE is prevalent in community-dwelling adults without clinically recognized cardiovascular disease and associated with future hospitalized HF.

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

BACKGROUND

B-type natriuretic peptides (BNPs) are used clinically to diagnose and monitor heart failure and are present in the circulation as multiple proBNP-derived fragments. We investigated the specificity of BNP immunoassays with glycosylated and nonglycosylated BNP, N-terminal proBNP (NT-proBNP), and proBNP peptides to probe the cross-reactivity of each assay.

METHODS

Nine B-type natriuretic peptides were studied,including synthetic and recombinant BNP (Shionogi, Scios, Mayo), human and synthetic glycosylated and nonglycosylated NT-proBNP (HyTest, Roche Diagnostics), and human glycosylated and nonglycosylated proBNP (HyTest, Scios). Five BNP [Abbott, Abbott POC, Alere, Beckman Coulter, Siemens (Centaur)], 9 NT-proBNP [Ortho-Clinical Diagnostics, Roche, Response, bioMerieux, Siemens (Dimension, Immulite, Stratus CS), Mitsubishi] and 3 research-use-only proBNP immunoassays [Biosite (Alere), Bio-Rad, Goetze] were evaluated. Specificity was assessed by calculating the recovery between baseline and peptide-spiked human plasma pools at target concentrations of 100 ng/L BNP, 300 ng/L proBNP, or 450 ng/L NT-proBNP. All assays were performed in duplicate.

RESULTS

BNP and NT-proBNP assays demonstrated substantial cross-reactivity with proBNP peptides. NT-proBNP assays do not detect glycosylated forms of either NT-proBNP or proBNP. proBNP assays preferentially detect the BNP 1-32 peptide and have minimal cross-reactivity with BNP peptides and glycosylated proBNP.

CONCLUSIONS

BNP or NT-proBNP results are not transferable among the current existing immunoassays owing to their differences in cross-reactivity and ability to detect various glycosylated forms of proBNP-derived fragments. Opportunities remain to standardize and harmonize BNP and NT-proBNP assays, as well as to develop specific proBNP assays, to widen their clinical scope of use.

Serial measurement of N-terminal pro-B-type natriuretic peptide and cardiac troponin T for cardiovascular disease risk assessment in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

N-terminal-pro-B-type natriuretic peptide (NT-proBNP) and cardiac troponin T (TnT) predict cardiovascular disease (CVD) risk in a variety of populations. Whether their predictive value varies by ethnicity is unknown. We sought to determine whether NT-proBNP and TnT improve prediction of incident coronary heart disease (CHD) and CVD, independent of CVD risk factors, in a multiethnic population; whether NT-proBNP improves prediction compared with the Framingham Risk Score or the Pooled Cohort Risk Equation; and whether a second NT-proBNP further improves prediction.

METHODS

Both NT-proBNP and TnT were measured in 5,592 MESA white, black, Hispanic, and Chinese participants (60% nonwhite; mean age 62.3 ± 10.3 years) in 2000 to 2002 and 2004 to 2005. We evaluated adjusted risk of incident CHD and CVD based on baseline and change in biomarker concentration.

RESULTS

Participants were followed up through 2011 and incurred 370 CVD events (232 CHD). Concentrations of NT-proBNP and TnT varied by ethnicity. Both NT-proBNP and TnT were associated with an increased risk of events (adjusted hazard ratio [HR] for CHD [95% CI] for fifth quintile vs other 4 quintiles of NT-proBNP, 2.03 [1.50-2.76]; HR for CHD for detectable vs undetectable TnT, 3.95 [2.29-6.81]). N-terminal-pro-B-type natriuretic peptide improved risk prediction and classification compared with the Framingham Risk Score and the Pooled Cohort Risk Equation. Change in NT-proBNP was independently associated with events (HR for CHD per unit increase in ΔlogNT-proBNP, 1.95 [1.16-3.26]). None of the observed associations varied by ethnicity.

CONCLUSIONS

Both NT-proBNP and TnT are predictors of incident CHD, independent of established risk factors and ethnicity, in a multiethnic population without known CVD. Change in NT-proBNP may add additional prognostic information.

NT-proBNP in cardiopulmonary resuscitated patients treated with mild therapeutic hypothermia is not independently associated with mortality: a retrospective observational study

Background

In spite of the introduction of mild therapeutic hypothermia (MTH), mortality rates remain high in patients with return of spontaneous circulation (ROSC) after cardiac arrest (CA). To date, no accurate and independent biomarker to predict survival in these patients exists. B-type natriuretic peptide (BNP) was found to provide both prognostic and diagnostic value in various cardiovascular diseases, including survival to hospital discharge in patients with ROSC. However, the biologically inactive counterpart of BNP, NT-proBNP, was found to be a more stable and accurate analyte. The current retrospective observational study investigates the value of NT-proBNP to predict 28-day mortality in post-CA patients treated with MTH, as well as the dynamics of NT-proBNP during MTH.

Methods

NT-proBNP levels were measured in post-CA patients cooled via cold intravenous saline infusion and water-circulating body wraps (Medi-Therm®, Gaymar). Plasma samples were obtained before cooling was started, at the start and end of the maintenance phase and at the end of rewarming.

Results

250 patients, admitted between 2009 and 2013, had NT-proBNP levels measured on ICU admission and were included for the evaluation of NT-proBNP as a prognostic marker. In the 28 days following ICU admission, 114 patients died (46%). Non-survivors had significantly higher NT-proBNP (median 1448 ng/l, IQR 366–4623 vs median 567 ng/1, IQR 148–1899; P < 0.001) levels on ICU admission. Unadjusted odds ratios for 28-day mortality were 1.7 (95% CI 0.8-3.5), 1.6 (0.8-3.3) and 3.6 (1.7-7.5) for increasing quartiles of NT-proBNP as compared to the lowest quartile. Adjusted odds ratios were 1.1 (95% CI 0.5-2.5), 1.1 (0.5-2.5) and 1.6 (0.7-3.8), respectively. A cut-off value of 834 ng/l achieved a sensitivity of 58% and a specificity of 58% to predict 28-day mortality. Of 113 patients, NT-proBNP values of each MTH phase were available and grouped in decreased or increased levels in time. Both decreases and increases of NT-proBNP values were observed during the MTH phases, but presence of either was not associated with outcome.

Conclusions

High NT-proBNP plasma concentrations on ICU admission are associated with high 28-day mortality in post-CA patients treated with MTH in a univariate analysis, but not in a multivariate analysis. Increases or decreases of NT-proBNP levels during MTH appear unrelated to 28 day mortality.

A multimarker approach to diagnose and stratify heart failure

BACKGROUND

We have previously demonstrated that circulating NT-proBNP is truncated at the N and C termini. Aims of this study are three-fold: firstly to determine whether the NT-proBNP levels correlate with NYHA functional classes when measuring with different antibody pairs; secondly to evaluate the diagnostic potential of ProBNP and; thirdly to investigate whether combining NT-proBNP assays with or without ProBNP would lead to better diagnostic accuracies.

METHODS

Plasma samples were collected from healthy controls (n=52) and HF patients (n=46). Customized AlphaLISA® immunoassays were developed and validated to measure the concentrations of proBNP and NT-proBNP (with antibodies targeting 13-45, 13-76, 28-76). The diagnostic performance and predictive value of proBNP and NT-proBNP assays and their combinations were evaluated.

RESULTS

Plasma proBNP assay showed acceptable diagnostic performance. NT-proBNP13-76 assay is useful in diagnosing and stratifying HF patients. The diagnostic performance of NT-proBNP13-76 demonstrated improvement over commercial NT-proBNP tests. The combination of NT-proBNP13-76 with NT-proBNP28-76 assays gave the best diagnostic assay performance.

CONCLUSION

Our results demonstrate that while there is major heterogeneity in circulating NT-proBNP, specific epitopes of the peptides are extraordinarily stable, providing ideal targets for clinically useful diagnostic assays. Future new clinical diagnostic clinical trials should include a multimarker approach rather than using a single marker to diagnose HF.

Cautious application of pleural N-terminal pro-B-type natriuretic peptide in diagnosis of congestive heart failure pleural effusions among critically ill patients

Background and Objective

Several studies on diagnostic accuracy of pleural N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) for effusions from congestive heart failure (CHF) conclude that pleural NT-pro-BNP is a useful biomarker with high diagnostic accuracy for distinguishing CHF effusions. However, its applicability in critical care settings remains uncertain and requires further investigations.

Methods

NT-proBNP was measured in pleural fluid samples of a prospective cohort of intensive care unit patients with pleural effusions. Receiver operating characteristic curve analysis was performed to determine diagnostic accuracy of pleural NT-proBNP for prediction of CHF effusions.

Results

One hundred forty-seven critically ill patients were evaluated, 38 (26%) with CHF effusions and 109 (74%) with non-CHF effusions of various causes. Pleural NT-proBNP levels were significantly elevated in patients with CHF effusions. Pleural NT-pro-BNP demonstrated the area under the curve of 0.87 for diagnosing effusions due to CHF. With a cutoff of 2200 pg/mL, pleural NT-proBNP displayed high sensitivity (89%) but moderate specificity (73%). Notably, 29 (27%) of 109 patients with non-CHF effusions had pleural NT-proBNP levels >2200 pg/mL and these patients were more likely to experience septic shock (18/29 vs. 10/80, P<0.001) or acute kidney injury (19/29 vs. 9/80, P<0.001).

Conclusions

Among critically ill patients, pleural NT-proBNP measurements remain a useful diagnostic aid in evaluation of pleural effusions. However, patients with non-CHF effusions may exhibit high pleural NT-proBNP concentrations if they suffer from septic shock or acute kidney injury. Accordingly, it is suggested that clinical context should be taken into account when interpreting pleural NT-proBNP values in critical care settings.

Placental expression of proBNP/NT-proBNP and plasma levels of NT-proBNP in early- and late-onset preeclampsia

BACKGROUND

Levels of plasma N-terminal pro B-type natriuretic peptide (NT-proBNP) are elevated in preeclampsia. In this study, the possibility that the placenta produces and releases proBNP/NT-proBNP was explored. Plasma levels of NT-proBNP in early- and late-onset preeclampsia were also measured.

METHODS

Placental proBNP mRNA in early-onset preeclampsia (n = 7), late-onset preeclampsia (n = 8), and controls of similar gestational age (n = 10) was assessed by quantitative real-time polymerase chain reaction. ProBNP/NT-proBNP protein was studied in placental samples with immunohistochemistry (n = 8) and tissue culture (n = 2). Plasma levels of NT-proBNP were measured in early-onset preeclampsia (n = 18), late-onset preeclampsia (n = 20), and relevant controls (n = 36).

RESULTS

Transcripts of proBNP mRNA were found in 20 out of 25 samples, there were no differences in expression between the groups. ProBNP/NT-proBNP protein was observed in maternal spiral arteries and in syncytiotrophoblasts in all placental samples. After placental tissue culture, there were measurable amounts of NT-proBNP in the culture media. Women with both early- (365 [14-9815] pg/ml) and late-onset preeclampsia (176 [33-2547] pg/ml) had higher levels of NT-proBNP than their controls (P < 0.001). There was a tendency toward higher levels of NT-proBNP in women with early-onset preeclampsia than in women with late-onset preeclampsia (P = 0.057).

CONCLUSION

The results indicate possible placental production and release of proBNP/NT-proBNP into the maternal circulation.

B-type natriuretic peptides for the prediction of cardiovascular events in patients with stable coronary heart disease: the Heart and Soul Study

Background

Brain‐type natriuretic peptide (BNP) and the amino‐terminal fragment of its prohormone (NT‐proBNP) are known predictors of cardiovascular outcomes in patients with coronary heart disease; however, the relative prognostic value of these 2 biomarkers for secondary events remains unclear.

Methods and Results

In 983 participants with stable coronary heart disease, we evaluated the association of BNP and NT‐proBNP with time to hospitalization for heart failure, nonfatal myocardial infarction, stroke or transient ischemic attack, cardiovascular death, and combined major adverse cardiovascular events (MACE). During an average follow‐up of 6.5±3.3 years, both BNP and NT‐proBNP were associated with increased risk of MACE in a multivariable‐adjusted model (hazard ratio per standard deviation of log BNP: 1.58; 95% CI: 1.32 to 1.89; hazard ratio per standard deviation of log NT‐proBNP: 1.84; 95% CI: 1.52 to 2.24). When added to traditional risk factors, NT‐proBNP predicted MACE better than BNP (C statistic: 0.76 versus 0.72, P<0.001). Similarly, the addition of NT‐proBNP resulted in a greater net reclassification improvement for predicting MACE than the addition of BNP (65% for NT‐proBNP, 56% for BNP).

Conclusions

Both BNP and NT‐proBNP were significant predictors of MACE in stable coronary heart disease; however, NT‐proBNP was superior to BNP for net risk reclassification for MACE.

Prognostic value of plasma N-terminal pro B-type natriuretic peptide levels in pneumonia patients requiring intensive care unit admission

BACKGROUND AND OBJECTIVE

Correct and early risk stratification for critically ill pneumonia patients remains an unmet medical need. This study aimed to test whether N-terminal pro B-type natriuretic peptide (NT-proBNP) can serve as a prognostic marker in this setting.

METHODS

This prospective study enrolled 216 pneumonia patients admitted to intensive care unit. Plasma NT-proBNP samples were obtained upon admission and primary outcome was all-cause mortality at 30 days. Meanwhile, Acute Physiology and Chronic Health Evaluation (APACHE) II and Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) 2007 minor criteria were assessed.

RESULTS

Overall 30-day mortality was 30%. NT-proBNP levels were significantly higher in nonsurvivors than survivors (11 938 ± 13 121 vs 5658 ± 9240 pg/mL, P = 0.001). Area under receiver operating characteristic curves of NT-proBNP, APACHE II and IDSA/ATS 2007 minor criteria were not significantly different regarding prediction of mortality (0.715, 0.754 vs 0.654, P = 0.085). Adding NT-proBNP to APACHE II significantly increased the area under receiver operating characteristic curve from 0.754 to 0.794 (P = 0.048). Receiver operating characteristic analysis revealed optimal NT-proBNP and APACHE II cut-offs of 2177.5 pg/mL and 25.5, respectively. In multivariate analysis, both NT-proBNP and APACHE II values above cut-offs had a significantly higher probability of death than those below cut-offs. A categorical approach combining NT-proBNP and APACHE II cut-offs provides additional risk stratification over a single marker approach.

CONCLUSIONS

For pneumonia patients admitted to intensive care unit, NT-proBNP strongly and independently predicts mortality, and its prognostic accuracy is comparable with APACHE II and IDSA/ATS 2007 minor criteria.

High-sensitivity cardiac troponin T and N-terminal pro-B-type natriuretic peptide predict mortality in stable coronary artery disease: results from the Ludwigshafen Risk and Cardiovascular Health (LURIC) study

BACKGROUND

The simultaneous assessment of high-sensitivity cardiac troponin T (hscTnT) and NT-proBNP for predicting death in stable coronary artery disease (CAD) has yet not been examined. We investigated the additional contribution of hscTnT to the risk of mortality prediction of NT-proBNP in patients with stable CAD.

METHODS

We studied 1469 patients with stable CAD enrolled in the Ludwigshafen Risk and Cardiovascular Health Study (LURIC). hscTnT and NT-proBNP were measured in baseline samples using immunoassays (Roche Diagnostics, Germany).

RESULTS

Thirty-five percent (n=525) of the patients died during a median follow-up of 7 and a half years. In total 59.0% of the non-survivors and 25.2% of the survivors exhibited concentrations of hscTnT≥14 ng/L. Logistic regression analysis identified hscTnT and NT-proBNP as independent risk markers for short-term (1-year follow-up) and long-term (9-years follow-up) mortality. ROC curve analysis determined optimal univariate cut-offs at 14 ng/L and 443 µg/L for hscTnT (AUC 0.725, p<0.0001) and NT-proBNP (AUC 0.742, p<0.0001), respectively. Kaplan-Meier survival analysis based on optimized cut-offs for the simultaneous determination of both biomarkers confirmed the usefulness of additive hscTnT especially in prediction of short-term mortality. The prognostic benefit of the combined assessment of hscTnT and NT-proBNP could be confirmed by a significantly increased reclassification index (NRI) of 24.2%.

CONCLUSIONS

The majority of non-survivors exhibited increased hscTnT concentrations above 14 ng/L. The simultaneous determination of NT-proBNP and hscTnT was superior for risk stratification compared to determining either marker alone. Especially the prediction of the clinically important 1-year mortality was significantly improved by addition of hscTnT to NT-proBNP.

The role of cardiac biomarkers in the diagnosis and management of patients presenting with suspected acute coronary syndrome

Myocardial infarction (MI) is the leading cause of death in the developed world. Biomarkers have an essential role in diagnosis, risk stratification, guiding management and clinical decision making in the setting of patients presenting with signs and symptoms of MI. Cardiac troponin (cTn) rose to prominence during the 1990s and has evolved to be the cornerstone for diagnosis of MI. The current criteria for MI diagnosis include a rise and/or fall in cTn with at least one value above the 99th percentile of the upper reference limit. Along with cTn, the natriuretic peptides B-type natriuretic peptide (BNP) and amino-terminal proBNP (NT-proBNP) have an important role in determining prognosis and guiding management. As assays for cTn have been evolved that are capable of reliably detecting smaller and smaller quantities in the blood, a dilemma has emerged as to how to use this new information. Several studies have attempted to answer this question and have shown that these lower concentrations of cTn have important prognostic significance and, more importantly, that intervention in these patients leads to improved clinical outcomes. New algorithms incorporating BNP, NT-proBNP, and more sensitive cTn assays hold promise for more rapid diagnosis or rule-out of MI, allowing for appropriate management steps to be initiated and more efficient and effective utilization of healthcare resources.

Cardiorenal syndrome is present in human fetuses with severe, isolated urinary tract malformations

OBJECTIVE

We analyzed the association between renal and cardiovascular parameters in fetuses with isolated severe urinary tract malformations.

METHODS

39 fetuses at a mean gestational age of 23.6 weeks with nephropathies or urinary tract malformations and markedly impaired or absent renal function were prospectively examined. Fetal echocardiography was performed, and thicknesses of the interventricular septum, and left and right ventricular wall were measured. Blood flow velocity waveforms of the umbilical artery, middle cerebral artery, and ductus venosus were obtained by color Doppler ultrasound. Concentrations of circulating n-terminal pro-B-type natriuretic peptide (nt-proBNP), cystatin C, ß2-microglobulin, and hemoglobin were determined from fetal blood samples.

RESULTS

Malformations included 21 cases of obstructive uropathy, 10 fetuses with bilateral nephropathy, and 8 cases of bilateral renal agenesis. Marked biventricular myocardial hypertrophy was present in all cases. The ratio between measured and gestational age-adjusted normal values was 2.01 (interventricular septum), 1.85, and 1.78 (right and left ventricular wall, respectively). Compared to controls, levels of circulating nt-proBNP were significantly increased (median (IQR) 5035 ng/L (5936 ng/L) vs. 1874 ng/L (1092 ng/L); p<0.001). Cystatin C and ß2-microglobulin concentrations were elevated as follows (mean ± SD) 1.85±0.391 mg/L and 8.44±2.423 mg/L, respectively (normal range 1.66±0.202 mg/L and 4.25±0.734 mg/L, respectively). No correlation was detected between cardiovascular parameters and urinary tract morphology and function. Despite increased levels of nt-proBNP cardiovascular function was preserved, with normal fetal Doppler indices in 90.2% of cases.

CONCLUSION

Urinary tract malformations resulting in severe renal impairment are associated with biventricular myocardial hypertrophy and elevated concentrations of circulating nt-proBNP during fetal life. Cardiovascular findings do not correlate with kidney function or morphology.

Amino terminal pro-B-type natriuretic peptide, secondary stroke prevention, and choice of antithrombotic therapy

BACKGROUND AND PURPOSE

Because of its association with atrial fibrillation and heart failure, we hypothesized that amino terminal pro-B-type natriuretic peptide (NT-proBNP) would identify a subgroup of patients from the Warfarin-Aspirin Recurrent Stroke Study, diagnosed with inferred noncardioembolic ischemic strokes, where anticoagulation would be more effective than antiplatelet agents in reducing risk of subsequent events.

METHODS

NT-proBNP was measured in stored serum collected at baseline from participants enrolled in Warfarin-Aspirin Recurrent Stroke Study, a previously reported randomized trial. Relative effectiveness of warfarin and aspirin in preventing recurrent ischemic stroke or death over 2 years was compared based on NT-proBNP concentrations.

RESULTS

About 95% of 1028 patients with assays had NT-proBNP below 750 pg/mL, and among them, no evidence for treatment effect modification was evident. For 49 patients with NT-proBNP >750 pg/mL, the 2-year rate of events per 100 person-years was 45.9 for the aspirin group and 16.6 for the warfarin group, whereas for 979 patients with NT-proBNP ≤750 pg/mL, rates were similar for both treatments. For those with NT-proBNP >750 pg/mL, the hazard ratio was 0.30 (95% confidence interval: 0.12-0.84; P=0.021) significantly favoring warfarin over aspirin. A formal test for interaction of NT-proBNP with treatment was significant (P=0.01).

CONCLUSIONS

For secondary stroke prevention, elevated NT-proBNP concentrations may identify a subgroup of ischemic stroke patients without known atrial fibrillation, about 5% based on the current study, who may benefit more from anticoagulants than antiplatelet agents. Clinical Trial Registration- This trial was not registered because enrollment began before 2005.

Biological variation and prognosis usefulness of new biomarkers in liver transplantation

An observational retrospective study has been conducted, including 52 patients (37 male and 15 female), ranging from 22 to 65 years old, who underwent an orthotopic liver transplantation (OLT) at the Hospital Universitario Central de Asturias (HUCA) between 2007 and 2010.

The main objective was to evaluate the post-OLT critical complication prognosis usefulness of the precursors of three new biomarkers: mid-regional proadrenomedullin (MR-proADM), carboxy-terminal-proendothelin-1 (CT-ProET-1) and mid-regional proatrial natriuretic peptide (MR-ProANP). As all of them are blood pressure mediators, stress-associated physiological phenomena are expected to affect their expression and secretion, mainly those related to blood circulation. Therefore, as a second goal, the biological variability of the biomarkers has been studied in a set of OLT patients without complications during the first postoperative week. The knowledge of the reference change value of the new biomarkers will be interesting for their correct interpretation in future investigations. The prognostic value of the new biomarkers was also compared to that of procalcitonin (PCT).

It has been shown that the basal concentration of the biomarkers is higher in patients that undergo OLT than in the normal population, correlating with the severity of the pathology. The intra-individual biological variation of these biomarkers is similar to other biochemical parameters, the reference change value for OLT patients being 90% for CT-proET-1, 112% for MR-proADM and 127% for MR-proANP.

Multivariate analysis showed that MR-proADM was the best biomarker for the prognosis of severe complications.

Circulating N-terminal pro-B-type natriuretic peptide in fetal anemia before and after treatment

BACKGROUND

N-terminal pro-B-type natriuretic peptide (ntproBNP) is an established marker of heart failure in adult cardiology. We analyzed nt-proBNP in the circulation of fetuses with increased volume load secondary to anemia and investigated the effect of treatment on nt-proBNP concentration.

METHODS

Fetuses undergoing intrauterine transfusion (IUT) were examined. nt-proBNP was measured before IUT and correlated with hemoglobin concentrations, ultrasonographic findings, and Doppler measurements of the peak systolic velocity of the middle cerebral artery (MCA-PSV).

RESULTS

A total of 27 patients (7 with hydrops) and 78 controls were examined. nt-proBNP was markedly elevated in anemia (P < 0.001). Concentrations were highest in hydropic fetuses (P < 0.03); no differences were present in hemoglobin and MCA-PSV values between hydropic and nonhydropic cases. In fetuses undergoing multiple IUTs nt-proBNP normalized after the third IUT, whereas hemoglobin and MCA-PSV remained abnormal.

CONCLUSION

Levels of circulating nt-proBNP correlate well with the degree of myocardial workload in the hyperdynamic state of fetal anemia. We hypothesize that normalization of nt-proBNP after serial transfusions is an indicator of myocardial adjustment to chronic anemia. nt-proBNP measurement may be useful in the management of fetal anemia, particularly in cases at risk of hydrops and fetuses requiring multiple transfusions.

Predictive value of depressive symptoms and B-type natriuretic peptide for new-onset heart failure and mortality

Depression and natriuretic peptides predict heart failure (HF) progression, but the unique contributions of depression and biomarkers associated with HF outcomes are not known. The present study determined the additive predictive value of depression and aminoterminal pro-B-type natriuretic peptide (NT-proBNP) for new-onset HF in HF-free subjects and mortality in patients with HF. The participants in the Cardiovascular Health Study were assessed for depressive symptoms using the Center for Epidemiologic Studies Depression Scale and NT-proBNP using an electrochemiluminescence immunoassay. The validated cutoff values for depression (Center for Epidemiologic Studies Depression Scale ≥8) and NT-proBNP (≥190 pg/ml) were used. The risks of incident HF and mortality (cardiovascular disease-related and all-cause) were examined during a median follow-up of 11 years, adjusting for demographics, clinical factors, and health behaviors. In patients with HF (n = 208), depression was associated with an elevated risk of cardiovascular disease mortality (hazard ratios [HR] 2.07, 95% confidence interval [CI] 1.31 to 3.27) and all-cause mortality (HR 1.49, 95% CI 1.05 to 2.11), independent of the NT-proBNP level and covariates. The combined presence of depression and elevated NT-proBNP was associated with substantially elevated covariate-adjusted risks of cardiovascular disease mortality (HR 5.42, 95% CI 2.38 to 12.36) and all-cause mortality (HR 3.72, 95% CI 2.20 to 6.37). In the 4,114 HF-free subjects, new-onset HF was independently predicted by an elevated NT-proBNP level (HR 2.27, 95% CI 1.97 to 2.62) but not depression (HR 1.08, 95% CI 0.92 to 1.26) in covariate-adjusted analysis. In conclusion, depression and NT-proBNP displayed additive predictive value for mortality in patients with HF. These associations can be explained by complementary pathophysiologic mechanisms. The presence of both elevated depression and NT-proBNP levels might improve the identification of patients with HF with a high risk of mortality.

N-Terminal Pro-B-type Natriuretic Peptide Levels in the Korean General Population

Background and Objectives

B-type natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP) levels may serve as a useful marker of cardiovascular risk for screening of the general population. We evaluated reference levels and distribution of NT-proBNP in the Korean general population based on a large cohort study.

Subjects and Methods

We included 1,518 adult subjects (ages 40-69) of a community-based cohort from the Korea Rural Genomic Cohort (KRGC) Study. Thorough biochemical and clinical data were recorded for all subjects. Levels of NT-proBNP from all participants were determined. In order to determine normal reference levels, subjects with factors known to influence NT-proBNP levels were excluded.

Results

The characteristics of the cohort are described below; subjects were 41.2% male, and the mean age was 54.8±8.4 years. The distribution of risk factors for cardiovascular disease in the cohort included hypertension (25%), left ventricular hypertrophy by electrocardiography (ECG-LVH) (15%), hypercholestolemia (4.5%), smoking (32%), diabetes (10.9%), history of coronary heart disease (4.9%), history of heart failure (0.9%), symptoms of heart failure (6.1%), elevated serum creatinine (≥1.5, 3.7%), and severe obesity (body mass index >30 kg/m², 4.6%). The levels of NT-proBNP of all subjects are shown below; the mean was 60.1±42.1, and the median was 36.5 pg/mL. In addition, the levels of NT-proBNP of normal subjects (which did not have any risk factors, n=224) are shown below; the mean was 40.8, and the median was 32.1 pg/mL. In normal subjects, the NT-proBNP level was slightly higher in females (25.7±24.8 vs. 46.9±35.4, p<0.001). NT-proBNP level increased with age in both the normal population and the total population. There were no significant differences in NT-proBNP levels in subjects who smoked, or had diabetes mellitus, hypertension or ECG-LVH. However, in subjects with a history of congestive heart failure (CHF) (58.5±103.29 vs. 213.8±258.8, p<0.005), elevated serum creatinine levels (≥1.5 mg/dL, 146.2±98.2 vs. 54.3±38.1, p<0.001), or who were older (≥60, 48.4 vs. 84.2±139.5 pg/mL, p<0.05), the BNP level was higher. In addition, patients with more than 3 risk factors for CHF had higher BNP levels (risk 0: 40.8±34.0, 1-2: 57.4±93.2, ≥3: 85.0±152.9 pg/mL). NT-proBNP levels were also related with age, sex, urine albumin, serum Cr, and high sensitivity C-reactive protein (p<0.05).

Conclusion

We determined the reference value and distribution of NT-proBNP in the Korean adult general population. We also found that adjustments for the independent effects of age, sex and renal function appear necessary when determining cardiac risk based on proBNP levels.

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.

N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) for predicting silent myocardial ischaemia in type 2 diabetes mellitus independent of microalbuminuria

BACKGROUND

In the early identification of cardiovascular risk, it is essential to establish a biological marker for cardiac complications that is comparable to albuminuria for nephropathy. We tested the hypothesis that N-terminal pro-brain natriuretic peptide (NT-proBNP) might be a marker for silent myocardial ischaemia in diabetes.

METHODS

In forty consecutively recruited subjects without evident coronary artery disease, serum NT-proBNP was measured together with multi-slice computed tomography. With patients suspected of having significant coronary artery stenosis by multi-slice computed tomography, coronary angiography was performed. Silent myocardial ischaemia was defined as the presence of significant coronary artery stenosis with more than 50% luminal narrowing by angiography.

RESULTS

Thirteen patients (32.5%) had silent myocardial ischaemia. NT-proBNP levels were significantly higher in these patients (181.1 ± 43.8 versus 55.2 ± 9.7 pg/mL, p < 0.005) but HbA(1c), lipid profiles, and creatinine were similar in the two groups. Moreover, log NT-proBNP was identified as an independent predictor of silent myocardial ischaemia (R(2) = 0.502, p < 0.05) after adjustment for HbA(1c), creatinine, albuminuria, hypertension, hyperlipidaemia, or smoking. After stratifying patients by NT-proBNP, the upper tertile compared to the lowest tertile was significantly associated with silent myocardial ischaemia (odds ratio: 26.7, p < 0.05). Receiver operation characteristics analysis with a cut-off value of 52 pg/mL showed 92% sensitivity and 75% specificity for predicting silent myocardial ischaemia (positive predictive value 64.7%, negative predictive value 94.3%).

CONCLUSIONS

The outstandingly high negative predictive value of NT-proBNP enables us to focus on diabetic patients with occult coronary disease, independently of microalbuminuria.