Multicenter analytical performance evaluation of the Elecsys® proBNP assay

Bioactive adrenomedullin for assessment of venous congestion in heart failure

AIMS

Bioactive adrenomedullin (bio-ADM) is a vascular-derived peptide hormone that has emerged as a promising biomarker for assessment of congestion in decompensated heart failure (HF). We aimed to evaluate diagnostic and prognostic performance of bio-ADM for HF in comparison to amino-terminal pro-B-type natriuretic peptide (NT-proBNP), with decision thresholds derived from invasive haemodynamic and population-based studies.

METHODS AND RESULTS

Normal reference ranges for bio-ADM were derived from a community-based cohort (n = 5060). Correlations with haemodynamic data were explored in a cohort of HF patients undergoing right heart catheterization (n = 346). Mortality and decision cutoffs for bio-ADM was explored in a cohort of patients presenting in the ER with acute dyspnoea (n = 1534), including patients with decompensated HF (n = 570). The normal reference range was 8-39 pg/mL. The area under the receiver operating characteristic curve (AUROC) for discrimination of elevated mean right atrial pressure (mRAP) and pulmonary arterial wedge pressure (PAWP) was 0.74 (95% CI = 0.67-0.79) and 0.70 (95% CI = 0.64-0.75), respectively, with optimal bio-ADM decision cutoff of 39 pg/mL, concordant with cubic spline analyses. NT-proBNP discriminated PAWP slightly better than mRAP (AUROC 0.73 [95% CI = 0.68-0.79] and 0.68 [95% CI = 0.61-0.75]). Bio-ADM correlated with (mRAP, r = 0.55) while NT-proBNP correlated with PAWP. Finally, a bio-ADM decision cutoff of 39 pg/mL associated with 30 and 90 day mortality and conferred a two-fold increased odds of HF diagnosis, independently from NT-proBNP.

CONCLUSIONS

Bio-ADM tracks with mRAP and associates with measures of systemic congestion and with mortality in decompensated HF independently from NT-proBNP. Our findings support utility of bio-ADM as a biomarker of systemic venous congestion in HF and nominate a decision threshold.

Skeletal Muscle Disorders: A Noncardiac Source of Cardiac Troponin T

BACKGROUND

Cardiac troponin (cTn) T and cTnI are considered cardiac specific and equivalent in the diagnosis of acute myocardial infarction. Previous studies suggested rare skeletal myopathies as a noncardiac source of cTnT. We aimed to confirm the reliability/cardiac specificity of cTnT in patients with various skeletal muscle disorders (SMDs).

METHODS

We prospectively enrolled patients presenting with muscular complaints (≥2 weeks) for elective evaluation in 4 hospitals in 2 countries. After a cardiac workup, patients were adjudicated into 3 predefined cardiac disease categories. Concentrations of cTnT/I and resulting cTnT/I mismatches were assessed with high-sensitivity (hs-) cTnT (hs-cTnT-Elecsys) and 3 hs-cTnI assays (hs-cTnI-Architect, hs-cTnI-Access, hs-cTnI-Vista) and compared with those of control subjects without SMD presenting with adjudicated noncardiac chest pain to the emergency department (n=3508; mean age, 55 years; 37% female). In patients with available skeletal muscle biopsies, TNNT/I1-3 mRNA differential gene expression was compared with biopsies obtained in control subjects without SMD.

RESULTS

Among 211 patients (mean age, 57 years; 42% female), 108 (51%) were adjudicated to having no cardiac disease, 44 (21%) to having mild disease, and 59 (28%) to having severe cardiac disease. hs-cTnT/I concentrations significantly increased from patients with no to those with mild and severe cardiac disease for all assays (all P<0.001). hs-cTnT-Elecsys concentrations were significantly higher in patients with SMD versus control subjects (median, 16 ng/L [interquartile range (IQR), 7-32.5 ng/L] versus 5 ng/L [IQR, 3-9 ng/L]; P<0.001), whereas hs-cTnI concentrations were mostly similar (hs-cTnI-Architect, 2.5 ng/L [IQR, 1.2-6.2 ng/L] versus 2.9 ng/L [IQR, 1.8-5.0 ng/L]; hs-cTnI-Access, 3.3 ng/L [IQR, 2.4-6.1 ng/L] versus 2.7 ng/L [IQR, 1.6-5.0 ng/L]; and hs-cTnI-Vista, 7.4 ng/L [IQR, 5.2-13.4 ng/L] versus 7.5 ng/L [IQR, 6-10 ng/L]). hs-cTnT-Elecsys concentrations were above the upper limit of normal in 55% of patients with SMD versus 13% of control subjects (P<0.01). mRNA analyses in skeletal muscle biopsies (n=33), mostly (n=24) from individuals with noninflammatory myopathy and myositis, showed 8-fold upregulation of TNNT2, encoding cTnT (but none for TNNI3, encoding cTnI) versus control subjects (n=16, P_Wald<0.001); the expression correlated with pathological disease activity (R=0.59, P_t-statistic<0.001) and circulating hs-cTnT concentrations (R=0.26, P_t-statistic=0.031).

CONCLUSIONS

In patients with active chronic SMD, elevations in cTnT concentrations are common and not attributable to cardiac disease in the majority. This was not observed for cTnI and may be explained in part by re-expression of cTnT in skeletal muscle.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03660969.

Evaluation of a multimarker panel in chronic heart failure: a 10-year follow-up

Aim: We assessed the 10-year prognostic role of 11 biomarkers with different pathophysiological backgrounds. Materials & methods/results: Blood samples from 144 patients with heart failure were analyzed. After 10 years of follow-up (median follow-up was 104 months), data regarding all-cause mortality were acquired. Regarding Kaplan-Meier analysis, all markers, except TIMP-1 and GDF-15, were significant predictors for all-cause mortality. We created a multimarker model with nt-proBNP, hs-TnT and IGF-BP7 and found that patients in whom all three markers were elevated had a significantly worse long-time prognosis than patients without elevated markers. Conclusion: In a 10-year follow-up, a combination of three biomarkers (NT-proBNP, hs-TnT, IGF-BP7) identified patients with a high risk of mortality.

Pre-analytical considerations in biomarker research: focus on cardiovascular disease

Clinical biomarker research is growing at a fast pace, particularly in the cardiovascular field, due to the demanding requirement to provide personalized precision medicine. The lack of a distinct molecular signature for each cardiovascular derangement results in a one-size-fits-all diagnostic and therapeutic approach, which may partially explain suboptimal outcomes in heterogeneous cardiovascular diseases (e.g., heart failure with preserved ejection fraction). A multidimensional approach using different biomarkers is quickly evolving, but it is necessary to consider pre-analytical variables, those to which a biological sample is subject before being analyzed, namely sample collection, handling, processing, and storage. Pre-analytical errors can induce systematic bias and imprecision, which may compromise research results, and are easy to avoid with an adequate study design. Academic clinicians and investigators must be aware of the basic considerations for biospecimen management and essential pre-analytical recommendations as lynchpin for biological material to provide efficient and valid data.

The role of age-specific N-terminal pro-brain natriuretic peptide cutoff values in predicting intravenous immunoglobulin resistance in Kawasaki disease: a prospective cohort study

BACKGROUND

The prediction of resistance to intravenous immunoglobulins (IVIG) is currently still one of the main research areas in Kawasaki disease (KD). Several studies have reported on the use of N-terminal pro-brain natriuretic peptide (NT-ProBNP) to this end. However, considering the age-dependency of NT-ProBNP levels, age- specific NT-ProBNP cutoff levels to predict IVIG resistance in KD might be more precise and should be evaluated.

METHODS

A prospective cohort study with standardized data collection involving 393 KD patients aged 1 month to 125 months was conducted between June 2015 and April 2018. The demographic characteristics, clinical manifestations and laboratory data were compared between the patients responding to initial intravenous immunoglobulin (IVIG-response group) and those who did not (IVIG-resistance group). We further distinguished four subgroups according to patients' age (< 1 year, 1-2 years, 2-6 years, > 6 years). The cutoff values of NT-ProBNP for the prediction of IVIG resistance overall and in the subgroups were obtained using receiver operating characteristic (ROC) analysis.

RESULTS

In all KD patients, the level of NT-ProBNP was significantly higher in the IVIG-resistance compared to the IVIG-response group (P = 0.006). This findings was similar in the subgroups except for patients older than six years. The best cutoff values of NT-ProBNP to predict IVIG resistance were 3755 pg/ml for all KD patients, 3710 pg/ml, 2800 pg/ml, 2480 pg/ml for those aged 2-6 years, 1-2 years and < 1 year, respectively. The corresponding sensitivities were 44.0, 52.2, 50.0 and 75.0%, while the specifities were 84.1, 86.3, 77.9 and 71.8%, respectively.

CONCLUSIONS

NT-proBNP is a complementary laboratory marker for the prediction of IVIG resistance in KD patients, particularly for those younger than one year. Applying age-specific cutoff values is more precise than one value for all ages.

Effect of coenzyme Q10 in Europeans with chronic heart failure: A sub-group analysis of the Q-SYMBIO randomized double-blind trial

BACKGROUND

Geographical differences in patient characteristics, management and outcomes in heart failure (HF) trials are well recognized. The aim of this study was to assess the consistency of the treat- ment effect of coenzyme Q10 (CoQ10) in the European sub-population of Q-SYMBIO, a randomized double-blind multinational trial of treatment with CoQ10, in addition to standard therapy in chronic HF.

METHODS

Patients with moderate to severe HF were randomized to CoQ10 300 mg daily or placebo in addition to standard therapy. At 3 months the primary short-term endpoints were changes in New York Heart Association (NYHA) functional classification, 6-min walk test, and levels of N-terminal pro-B type natriuretic peptide. At 2 years the primary long-term endpoint was major adverse cardiovascular events (MACE).

RESULTS

There were no significant changes in short-term endpoints. The primary long-term endpoint of MACE was reached by significantly fewer patients in the CoQ10 group (n = 10, 9%) compared to the placebo group (n = 33, 27%, p = 0.001). The following secondary endpoints were significantly improved in the CoQ10 group compared with the placebo group: all-cause and cardiovascular mortality, NYHA classification and left ventricular ejection fraction (LVEF). In the European sub-population, when compared to the whole group, there was greater adherence to guideline directed therapy and similar results for short- and long-term endpoints. A new finding revealed a significant improvement in LVEF.

CONCLUSIONS

The therapeutic efficacy of CoQ10 demonstrated in the Q-SYMBIO study was confirmed in the European sub-population in terms of safely reducing MACE, all-cause mortality, cardiovascular mortality, hospitalization and improvement of symptoms.

Minute Myocardial Injury as Measured by High-Sensitive Troponin T Serum Levels Predicts the Response to Intracoronary Infusion of Bone Marrow-Derived Mononuclear Cells in Patients With Stable Chronic Post-Infarction Heart Failure: Insights From the TOPCARE-CHD Registry

RATIONALE

Cell-based therapies are a promising option in patients with chronic postinfarction heart failure (ischemic cardiomyopathy [ICM]). However, the responses after intracoronary infusion of autologous bone marrow-derived mononuclear cells (BMCs) are heterogeneous, which may be related to impaired cell retention in patients with ICM. Ischemic injury is associated with upregulation of prototypical chemoattractant cytokines mediating retention and homing of circulating cells. The development of ultrasensitive tests to measure high-sensitive troponin T (hs-TnT) serum levels revealed the presence of ongoing minute myocardial injury even in patients with stable ICM.

OBJECTIVE

To test the hypothesis that serum levels of hs-TnT correlate with cell retention and determine the response to intracoronary BMC application in patients with ICM.

METHODS AND RESULTS

About 157 patients with stable ICM and no substantial impairment of kidney function received intracoronary BMC administration. Immediately prior to cell application, hs-TnT levels to measure myocardial injury and NT-proBNP levels as marker of left ventricular wall stress were determined. Patients with elevated hs-TnT were older and had more severe heart failure. Importantly, only patients with elevated baseline hs-TnT≥15.19 pg/mL (upper tertile) demonstrated a significant (P=0.04) reduction in NT-proBNP serum levels (-250 [-1465; 33] pg/mL; relative reduction -24%) 4 months after BMC administration, whereas NT-proBNP levels remained unchanged in patients in the 2 lower hs-TnT tertiles. The absolute decrease in NT-proBNP at 4 months was inversely correlated with baseline hs-TnT (r=-0.27, P=0.001). Finally, retention of intracoronarily infused, ¹¹¹Indium-labeled cells within the heart was closely associated with hs-TnT levels in patients with chronic ischemic heart failure (P=0.0008, n=10, triple measurements).

CONCLUSIONS

The extent of ongoing myocardial injury as measured by serum levels of hs-TnT predicts the reduction of NT-proBNP serum levels at 4 months after intracoronary BMC administration in patients with ICM, suggesting that the beneficial effects of BMC application on LV remodeling and wall stress are confined to patients with ongoing minute myocardial injury.

CLINICAL TRIAL REGISTRATION

URL: www.clinicaltrials.gov. Unique identifier: NCT00962364.

Early changes in left atrial volume after acute myocardial infarction. Relation to invasive hemodynamics at rest and during exercise

BACKGROUND

Dilatation of left atrium (LA) reflects chronic LA pressure or volume overload that possesses considerable prognostic information. Little is known regarding the interaction between LA remodeling after acute myocardial infarction (MI) and left atrial pressure at rest and during exercise. The objective was to assess changes in LA volume early after MI in patients with diastolic dysfunction and the relation to invasive hemodynamics and natriuretic peptides.

METHODS

62 patients with left ventricle ejection fraction (LVEF)≥45%, diastolic E/e'>8 and LA volume index >34ml/m² within 48h of MI were enrolled. After 1 and 4months blood sampling, echocardiography and right heart catheterization were performed during exercise test.

RESULTS

LA remodeling was considered in patients with a change from mild (35-41ml/m²), to severe (>48ml/m²) dilatation after 4months (Found in 22 patients (35%)). Patients with LA remodeling were characterized by lower a' (1month 8.9±2.0 vs. 10.4±2.5cm/s, p=0.002; 4month 8.8±2.0 vs. 10.4±2.4cm/s, p=0.007) and higher MR-proANP (1month 162±64 vs. 120±44pg/l, p=0.005; 4months 175±48 vs. 129±56pg/l, p=0.002). With exercise, pulmonary artery pressure, right atrial pressure and pulmonary capillary wedge pressure increased markedly in all patients. There were however, no significant differences in filling pressure at rest or during exercise irrespective of whether LA remodeling occurred.

CONCLUSION

Contrary to our hypothesis early LA dilatation after MI was weakly associated with resting and exercise induced changes in LA pressure overload. The dilatation was however associated with lower e' and higher MR-proANP.

N-terminal pro-B-type natriuretic peptide variability in stable dialysis patients

BACKGROUND AND OBJECTIVES

Monitoring N-terminal pro-B-type natriuretic peptide (NT-proBNP) may be useful for assessing cardiovascular risk in dialysis patients. However, its biologic variation is unknown, hindering the accurate interpretation of serial concentrations. The aims of this prospective cohort study were to estimate the within- and between-person coefficients of variation of NT-proBNP in stable dialysis patients, and derive the critical difference between measurements needed to exclude biologic and analytic variation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Fifty-five prevalent hemodialysis and peritoneal dialysis patients attending two hospitals were assessed weekly for 5 weeks and then monthly for 4 months between October 2010 and April 2012. Assessments were conducted at the same time in the dialysis cycle and entailed NT-proBNP testing, clinical review, electrocardiography, and bioimpedance spectroscopy. Patients were excluded if they became unstable.

RESULTS

This study analyzed 136 weekly and 113 monthly NT-proBNP measurements from 40 and 41 stable patients, respectively. Results showed that 22% had ischemic heart disease; 9% and 87% had left ventricular systolic and diastolic dysfunction, respectively. Respective between- and within-person coefficients of variation were 153% and 27% for weekly measurements, and 148% and 35% for monthly measurements. Within-person variation was unaffected by dialysis modality, hydration status, inflammation, or cardiac comorbidity. NT-proBNP concentrations measured at weekly intervals needed to increase by at least 46% or decrease by 84% to exclude change due to biologic and analytic variation alone with 90% certainty, whereas monthly measurements needed to increase by at least 119% or decrease by 54%.

CONCLUSIONS

The between-person variation of NT-proBNP was large and markedly greater than within-person variation, indicating that NT-proBNP testing might better be applied in the dialysis population using a relative-change strategy. Serial NT-proBNP concentrations need to double or halve to confidently exclude change due to analytic and biologic variation alone.

Relationships between biomarkers and left ventricular filling pressures at rest and during exercise in patients after myocardial infarction

BACKGROUND

Increased pulmonary capillary wedge pressure (PCWP) is an independent prognostic predictor after myocardial infarction (MI), but PCWP is difficult to assess noninvasively in subjects with preserved ejection fraction (EF). We hypothesized that biomarkers would provide information regarding PCWP at rest and during exercise in subjects with preserved EF after MI.

METHODS AND RESULTS

Seventy-four subjects with EF >45% and recent MI underwent right heart catheterization at rest and during a symptom-limited semisupine cycle exercise test with simultaneous echocardiography. Plasma samples were collected at rest for assessment of midregional pro-A-type natriuretic peptide (MR-proANP), N-terminal pro-B-type natriuretic peptide (NT-proBNP), galectin-3 (Gal-3), copeptin, and midregional pro-adrenomedullin (MR-proADM). Plasma levels of MR-proANP and PCWP were associated at rest (r = 0.33; P = .002) and peak exercise (r = 0.35; P = .002) as well as with changes in PCWP (r = 0.26; P = .03). Plasma levels of NT-proBNP and PCWP were weakly associated at rest (r = 0.23; P = .03) and peak exercise (r = 0.28; P = .02) but not with changes in PCWP (r = 0.20; P = .09). In a multivariable analysis, plasma levels of MR-proANP remained associated with rest and exercise PCWP (P < .01), whereas NT-proBNP did not. Plasma levels of Gal-3, copeptin, and MR-proADM were not associated with PCWP at rest or peak exercise.

CONCLUSIONS

In subjects recovering from an acute MI with preserved EF, plasma levels of natriuretic peptides, particularly MR-proANP, are associated with filling pressures at rest and during exercise.

Comprehensive biomarker profiling in patients with obstructive sleep apnea

OBJECTIVES

The pathophysiological links between obstructive sleep apnea syndrome (OSAS) and cardiovascular mortality are incompletely understood. We aimed to contribute to a better characterization by using comprehensive biomarker profiling quantifying hemodynamic cardiac stress, cardiomyocyte injury, inflammation, endothelial function, matrix turnover and metabolism.

DESIGN AND METHODS

In 65 patients with moderate or severe OSAS [apnea-hypopnea index (AHI) 39±20/h] and 33 patients with no or mild OSAS (AHI 8+4/h), B-type natriuretic peptide (BNP), N-terminal-pro-BNP (NT-proBNP), high-sensitivity cardiac troponin I (hs-cTnI), interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), matrix metalloproteinase-9 (MMP-9), and insulin were measured before and after sleep. In a subgroup measurements were repeated in a second night with continuous positive airway pressure (CPAP).

RESULTS

Patients with moderate/severe OSAS had higher insulin before sleep [median (interquartile range), 36.4 (21.9-52.1) vs. 20.8 (10.6-32.8)mU/mL; p=0.006], higher IL-6 after sleep [1.00 (0.73-1.58) vs. 0.72 (0.48-0.94)pg/mL; p=0.005], and larger relative overnight reduction in BNP [-9 (-35-0) vs. -3 (-21-13)%; p=0.04] than those with mild/no OSAS. Insulin before sleep was the only independent predictor of moderate/severe OSAS. Insulin before and IL-6 after sleep were independent predictors of severe OSAS, and when combined provided high diagnostic accuracy for severe OSAS (area under the receiver operator characteristic curve 0.80; 95%-confidence interval 0.69-0.91). In contrast, there were no significant differences in NT-proBNP, hs-cTnI, VEGF, and MMP-9 between moderate/severe and mild/no OSAS. Short-term CPAP had no impact on biomarker concentrations before and after sleep.

CONCLUSIONS

Significant OSAS is characterized by a distinct biomarker profile including high insulin before and high IL-6 after sleep.

Panel of emerging cardiac biomarkers contributes for prognosis rather than diagnosis in chronic heart failure

Background: As complex disease, heart failure is associated with various pathophysiological and biochemical disorders. No single biomarker is able to display all these characteristics. Therefore, we evaluated a multimarker panel together with the biochemical gold-standard NT-proBNP. Part of the panel are markers for angiogenesis (Endostatin, IBP-4, IBP-7, sFlt-1 as antiangiogenetic factors and PLGF as angiogenectic factor), myocyte stress (GDF-15), extracellular matrix remodelling (galectin-3, mimecan and TIMP-1), inflammation (galectin-3) and myocyte injury (hs-TnT). Methods: All markers (Roche Diagnostics, Penzberg, Germany) were assessed in a cohort of 149 patients with chronic heart failure and 84 healthy controls. Results: All markers were positively correlated with ln NT-proBNP (each p < 0.05). Furthermore, they were significantly elevated in patients with chronic heart failure (each p < 0.05). All markers increased significantly with severity of LV dysfunction and severity of New York Heart Association class (each p < 0.05), except for PLGF and Mimecan (each p = NS). With the exception of endostatin, mimecan and PLGF, all other markers were further significant predictors for all-cause mortality in a 3-year follow-up. In a multimarker approach of the five biomarkers with the best performance (NT-proBNP, hs-TnT, TIMP-1, GDF-15 and IBP-4), the event rate was superior to NT-proBNP alone and increased significantly and progressively with the number of elevated biomarkers. Conclusion: All emerging markers increased stepwise with the severity of symptoms and LV dysfunction and offer important prognostic information in chronic heart failure, except for PLGF and mimecan. Five biomarkers with different pathophysiological background incorporated additive prognostic value in heart failure. Prognostication in heart failure may be further improved through a multimarker approach.

Preliminary Development of a DNA Aptamer-Magnetic Bead Capture Electrochemiluminescence Sandwich Assay for Brain Natriuretic Peptide

Fifty-two candidate DNA aptamer sequences were selected for binding to the cardiovascular biomarker B-type or brain natriuretic peptide (BNP). Candidate aptamers were screened to rank their relative affinities against BNP by an aptamer-based ELISA-like aptamer microplate assay (ELASA). The highest affinity aptamers from ELASA screening were also paired in all possible combinations and screened for electrochemiluminescence (ECL) assay potential in capture aptamer-magnetic bead and ruthenium trisbipyridine (Ru(bpy)₃²⁺)-reporter aptamer sandwich formats. The top ECL sandwich combinations utilized the same aptamer pair in either capture or reporting roles with nanogram to low picogram per mL levels of detection even in 50% human serum. ECL assay sensitivity and linearity even in 50% human serum suggest that the aptamer-based assay is at least comparable to other reported immunoassays for BNP.

Do laboratories follow heart failure recommendations and guidelines and did we improve? The CARdiac MArker Guideline Uptake in Europe (CARMAGUE)

BACKGROUND

Natriuretic peptides (NP) are well-established markers of heart failure (HF). During the past 5 years, analytical and clinical recommendations for measurement of these biomarkers have been published in guidelines. The aim of this follow-up survey was to investigate how well these guidelines for measurement of NP have been implemented in laboratory practice in Europe.

METHODS

Member societies of the European Federation of Clinical Chemistry and Laboratory Medicine were invited in 2009 to participate in a web-based audit questionnaire. The questionnaire requested information on type of tests performed, decision limits for HF, turn-around time and frequency of testing.

RESULTS

There was a moderate increase (12%) of laboratories measuring NP compared to the initial survey in 2006. The most frequently used HF decision limits for B-type NP (BNP) and N-terminal BNP (NT-proBNP) were, respectively, 100 ng/L and 125 ng/L, derived from the package inserts in 55%. Fifty laboratories used a second decision limit. Age or gender dependent decision limits were applied in 10% (8.5% in 2006). The vast majority of laboratories (80%) did not have any criteria regarding frequency of testing, compared to 33% in 2006.

CONCLUSIONS

The implementation of NP measurement for HF management was a slow process between 2006 and 2009 at a time when guidelines had just been established. The decision limits were derived from package insert information and literature. There was great uncertainty concerning frequency of testing which may reflect the debate about the biological variability which was not published for most of the assays in 2009.

The biological variation of N-terminal pro-brain natriuretic peptide in postmenopausal women with type 2 diabetes: a case control study

BACKGROUND

The incidence of heart failure in type 2 diabetes is high and it has poorer prognosis when compared with patients without diabetes. Access to echocardiography is limited and alternative methods to identify early heart failure such as the measurement of natriuretic peptides levels have been proposed. However, their wide biological variation could limit their clinical utility. Our aim was to determine if the intrinsic biological variation of one of these peptides, N-terminal proBNP, is as wide in type 2 diabetes as it is in health and to calculate the critical difference values that could be utilised in clinical practice to ensure changes observed between two samples are due to intervention rather than to its biological variability.

METHODOLOGY/PRINCIPAL FINDINGS

12 postmenopausal women with diet controlled type 2 diabetes and without heart failure were compared with 11 control postmenopausal women without diabetes. N-terminal proBNP levels were measured on 10 occasions. The biological variation was calculated according to Fraser's methods. The mean NT-proBNP level was similar in both groups (mean ± standard deviation; type 2 diabetes, 10.7 pmol/L± 8.5 versus 8.49±6.0 pmol/L, p = 0.42). The biological variation was also similarly wide. The critical difference in patients with type 2 diabetes was between -70% and ±236%.

CONCLUSIONS

Type 2 diabetes does not appear to significantly influence the marked biological variation of N-terminal proBNP in postmenopausal women. The critical difference values reported in this study could be used to titrate therapy or monitor response to interventions although the change required in between samples is wide and this might limit its utility.

Levels of NT-proBNP, markers of low-grade inflammation, and endothelial dysfunction during spironolactone treatment in patients with diabetic kidney disease

Renin-angiotensin-aldosterone system (RAAS) blockade may reduce levels of biomarkers of chronic low-grade inflammation and endothelial dysfunction. We investigated the effect of spironolactone added to standard RAAS blockade on these biomarkers in an analysis of four original studies.

MATERIALS AND METHODS

The studies were double-blind, randomised, placebo-controlled studies in 46 type 1 and 23 type 2 diabetic patients with micro- or macroalbuminuria treated with angiotensin-converting enzyme inhibitor (ACE inhibitor) or angiotensin receptor blocker (ARB), and randomised to additional treatment with spironolactone 25 mg and placebo daily for 60 days.

OUTCOME MEASURES

Changes in inflammatory (hsCRP, s-ICAM, TNFα, IL-6, IL-8, Serum amyloid A, IL1β), endothelial dysfunction (sE-selectin, s-ICAM1, s-VCAM1, VWF, p-selectin, s-thrombomodulin) and NT-proBNP after each treatment period.

RESULTS

During spironolactone treatment, u-albumin excretion rate was reduced from 605 (411-890) to 433 (295-636) mg/24 h, as previously reported. Markers of inflammation and endothelial dysfunction did not change; only changes in NT-proBNP (reduced by 14%, p=0.05) and serum amyloid A (reduced by 62%, p=0.10) were borderline significant.

DISCUSSIONS

Our results indicate that the renoprotective effect of spironolactone when added to RAAS blockade is not mediated through anti-inflammatory pathways since markers of inflammation and endothelial dysfunction are not affected during treatment.

Association of somatic and cognitive depressive symptoms and biomarkers in acute myocardial infarction: insights from the translational research investigating underlying disparities in acute myocardial infarction patients' health status registry

BACKGROUND

Somatic depressive symptoms and certain biomarkers are each associated with worse acute myocardial infarction (AMI) prognosis, but the relationship between depressive symptom domains and inflammatory, neurohormonal, and coagulation markers is unknown.

METHODS

We examined the relationship between depressive symptoms and 1-month biomarker levels (high-sensitivity C-reactive protein [hs-CRP], N-terminal pro-brain natriuretic peptide [NT-proBNP], white blood cell [WBC], platelet counts) in 1265 AMI patients. Depressive symptoms (9-item Patient Health Questionnaire) were assessed during index hospitalization and categorized as somatic or cognitive. Using median regression models, the upper quartile of somatic and cognitive depression scores and each biomarker were compared with the lower three quartiles, adjusting for site, demographics, and clinical characteristics.

RESULTS

Although hs-CRP values were higher in patients with somatic symptoms, this association was attenuated after adjustment (B(per SD increase) = .02, 95% confidence interval: .00; .05, p = .07). WBC count was independently associated with somatic depressive symptoms (B(per SD increase) = .28, 95% confidence interval: .12; .44, p < .001). Cognitive depressive symptoms were not associated with hs-CRP or WBC count. Neither dimension was associated with NT-proBNP or platelet levels. For each biomarker, the depression dimensions explained <1% of their variation.

CONCLUSIONS

Neither somatic nor cognitive depressive symptoms were meaningfully associated with hs-CRP, NT-proBNP, WBC, or platelet counts 1 month after AMI, suggesting that the association between depression and long-term outcomes may be unrelated to these biomarkers. Future research should explore other biomarkers to better illuminate pathways by which depression adversely impacts AMI prognosis.

HDR imaging evaluation of a NT-proBNP test with a mobile phone

The determination of NT-proBNP levels is key for the monitoring of patients with diagnosed heart failure and it is a routine measurement typically performed at health care centers, which would benefit from decentralized alternatives. Here we investigate the quantitative evaluation of a well-established NT-proBNP test using a standard mobile phone (Nokia 6720) as measuring platform rather than a dedicated instrument. A Java ME software developed for this application controls the illumination and imaging of the proBNP test under defined time intervals, which enables the composition of multi-exposure sets that are processed as high dynamic range (HDR) images for contrast enhancement. The results show that HDR processing significantly increases the sensitivity and resolution of the technique achieving a performance within the diagnostics range. These results demonstrate the feasibility to exploit a ubiquitous device to decentralize the evaluation of a routine test and identify key processing alternatives to bring the performance of such systems within the diagnostics range.

Hemodynamic determinants of myocardial B-type natriuretic peptide release: relative contributions of systolic and diastolic wall stress

Although B-type natriuretic peptide (BNP) is widely used as a biomarker for heart failure, the in vivo mechanical stimulus for its cardiac release remains poorly defined. We aimed to characterize the hemodynamic determinants of the transcardiac BNP gradient as a measure of myocardial BNP release by performing a detailed hemodynamic assessment in subjects with a broad spectrum of systolic and diastolic left ventricular dysfunction. Forty-two subjects underwent a detailed transthoracic echocardiographic study, right heart catheterization, and simultaneous BNP measurement in arterial and coronary sinus plasma. The transcardiac BNP gradient was lowest in subjects with normal left ventricular ejection fraction/high peak early diastolic annular velocity (n=11), intermediate in those with normal left ventricular ejection fraction/low peak early diastolic annular velocity (n=13), and highest in those with low left ventricular ejection fraction/low peak early diastolic annular velocity (n=18; 29 ng/L (range: 15 to 78 ng/L) versus 88 ng/L (range: 34 to 172 ng/L) versus 1566 ng/L (range: 624 to 2349 ng/L; P<0.001). Across the range of patients, left ventricular end-systolic wall stress (r(2)=0.51) and peak systolic mitral annular velocity (r(2)=0.47) showed the strongest correlation with higher transcardiac BNP gradient. In contrast, the transcardiac BNP gradient was weakly related to indices of diastolic load, including pulmonary capillary wedge pressure (r(2)=0.27) and left ventricular end-diastolic wall stress (r(2)=0.21). Across this spectrum of pathophysiology, left ventricular end-systolic wall stress appears to be the key mechanical stimulus influencing cardiac BNP release.

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

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

Design and methodology of the NorthStar Study: NT-proBNP stratified follow-up in outpatient heart failure clinics -- a randomized Danish multicenter study

BACKGROUND

Randomized clinical trials have shown that newly discharged and symptomatic patients with chronic heart failure (CHF) benefit from follow-up in a specialized heart failure clinic (HFC). Clinical stable and educated patients are usually discharged from the HFC when on optimal therapy. It is unknown if risk stratification using natriuretic peptides could identify patients who would benefit from longer-term follow-up. Furthermore, data on the use of natriuretic peptides for monitoring of stable patients with CHF are sparse.

AIMS

The aims of this study are to test the hypothesis that clinical stable, educated, and medical optimized patients with CHF with N-terminal pro-brain natriuretic peptide (NT-proBNP) levels > or = 1,000 pg/mL benefit from long-term follow-up in an HFC and to assess the efficacy of NT-proBNP monitoring.

METHODS

A total of 1,250 clinically stable, medically optimized, and educated patients with CHF will be enrolled from 18 HFCs in Denmark. The patients will be randomized to treatment in general practice, to a standard follow-up program in the HFC, or to NT-proBNP monitoring in the HFC. The patients will be followed for 30 months (median).

RESULTS

Data will be collected from 2006 to 2009. At present (March 2008), 720 patients are randomized. Results expect to be presented in the second half of 2010.

CONCLUSIONS

This article outlines the design of the NorthStar study. If our hypotheses are confirmed, the results will help cardiologists and nurses in HFCs to identify patients who may benefit from long-term follow-up. Our results may also indicate whether patients with CHF will benefit from adding serial NT-proBNP measurements to usual clinical monitoring.

Myocardial tissue Doppler echocardiography and N-terminal B-type natriuretic peptide (NT-proBNP) in diastolic and systolic heart failure

Background

The aim of this prospective study was to assess the diagnostic value of NT-proBNP and the concordance with Tissue Doppler Echocardiography (including strain and longitudinal displacement) in diastolic and systolic heart failure.

Methods and results

137 consecutive clinically stable patients were included (42 healthy controls, 43 with diastolic heart failure, 52 with systolic heart failure). In diastolic heart failure, basal septal strain was reduced (-24.8 ± 8.1% vs. controls. -18.5 ± 5.3%, p < 0.0001). In all patients with preserved systolic function, septal basal longitudinal displacement was impaired in patients with increased left-ventricular filling pressures (E/E' < 8: 13.5 mm ± 3.3 mm vs. E/E' > 15: 8.5 mm ± 2.3 mm, p = 0.001) parallel to NT-proBNP elevation (E/E' < 8: 45.8 pg/ml, IQR: 172.5 pg/ml vs. E/E' > 15: 402.0 pg/ml, IQR: 1337.2 pg/ml; p = 0.0007). In ROC analysis, NT-proBNP could detect patients with reduced left ventricular systolic function (LVEF ≥ 55%) with a good diagnostic accuracy. However, the diagnostic accuracy of NT-proBNP to detect diastolic dysfunction was lower.

Conclusion

Subtle changes of longitudinal myocardial function begin in diastolic heart failure and are further increased in systolic heart failure. In patients with preserved LV function, a complex approach with the integration of multiple parameters including Tissue Doppler echocardiography and NT-proBNP is necessary to classify patients.

N-terminal pro-brain natriuretic peptide is a useful diagnostic marker for transfusion-associated circulatory overload

BACKGROUND

Transfusion-associated circulatory overload (TACO) can be difficult to diagnose and distinguish from transfusion-related acute lung injury (TRALI), but is a relatively common complication that occurs when increases in blood volume overwhelm the cardiovascular system. Brain natriuretic peptide (BNP) has been shown to be a functional marker for TACO. N-terminal pro-brain natriuretic peptide (NT-proBNP) is another marker that could be more helpful than BNP since it has a longer half-life in circulation and is also much more stable in laboratory samples. In this study, whether NT-proBNP is a useful diagnostic marker for TACO was evaluated.

STUDY DESIGN AND METHODS

Forty patients were enrolled into a case-control study (16 patients with TACO and 24 control patients) and had pre- and posttransfusion NT-proBNP concentrations evaluated from submitted type-and-screen blood samples.

RESULTS

The sensitivity of elevated posttransfusion NT-proBNP to diagnose TACO was 93.8 percent, the specificity was 83.8 percent, and the accuracy was 87.5 percent. Elevated posttransfusion NT-proBNP is the only independent variable for the diagnosis of TACO based on multivariate logistic regression.

CONCLUSION

NT-proBNP is both a sensitive and a specific marker for TACO and can be helpful in confirming transfusion associated fluid overload. This study also demonstrates that many patients who experience TACO may already be in a state of excess volume. Clinicians should be aware that many asymptomatic patients have excess fluid and transfusion may cause these patients to become symptomatic.

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

Amino-terminal pro-B-type natriuretic peptide (NT-proBNP) is a convenient molecule to work with in clinical laboratories, with preanalytic and analytic advantages, such as excellent stability at different temperatures, flexibility in sample type, and strong harmony across all commercially available NT-proBNP assays (including recently released point-of-care methods). Another major advantage of NT-proBNP assays is that they show excellent analytic precision. Reference values for NT-proBNP testing are strongly affected by the population tested. Among nondiseased populations, lower values are expected, whereas in diseased populations, such as in patients with acute dyspnea, higher reference values are more useful. Also, the biologic variability of NT-proBNP should be taken into account to evaluate the significance of any change in its values. When analyzed in patients with stable heart failure, biologic variability was 25%-40%. This article reviews the laboratory aspects of NT-proBNP testing from the perspective of the clinical laboratorian.

Prognostic usefulness of anemia and N-terminal pro-brain natriuretic peptide in outpatients with systolic heart failure

N-terminal pro-brain natriuretic peptide (NT-pro-BNP) and anemia are predictors of outcome in systolic heart failure. It is currently unclear how these 2 markers interact in particular with regard to the prognostic information carried by each risk marker. We therefore tested the hypothesis that anemia (World Health Organization criteria, hemoglobin levels <7.5 mmol/L for women and <8.0 mmol/L for men) and NT-pro-BNP are associated and evaluated how a possible association affects the prognostic value of each risk marker. Clinical data from 345 patients with systolic heart failure were obtained prospectively at the baseline visit to our heart failure clinic (inclusion criterion left ventricular ejection fraction <0.45, no exclusion criteria). Follow-up was 30 months (median), and 70 events (mortality) occurred. Prevalence of anemia was 27%. In a multivariate logistic regression model, anemia (p = 0.041) was closely associated with NT-pro-BNP levels above the median (1,381 pg/ml) after adjustment for traditional confounders (left ventricular ejection fraction, age, body mass index, atrial fibrillation, chronic kidney disease). In an adjusted Cox proportional hazard model, the 2 parameters were associated with mortality after adjustment for traditional confounders (hazard ratio for anemia 1.73, 95% confidence interval 1.06 to 2.83, p = 0.029; hazard ratio for NT-pro-BNP >1,381 pg/ml 2.68, 95% confidence interval 1.58 to 4.66, p <0.001). Patients with anemia and high NT-pro-BNP levels had a fivefold increased risk for mortality (hazard ratio 4.77, 95% confidence interval 2.47 to 9.18, p <0.001). In conclusion, anemia is closely associated with NT-pro-BNP in patients with systolic heart failure, and anemia and NT-pro-BNP carry independent prognostic information. Patients with anemia and high levels of NT-pro-BNP have a markedly increased mortality risk.

N-terminal pro-brain natriuretic peptide predicts myocardial ischemia and is related to postischemic left-ventricular dysfunction in patients with stable coronary artery disease

BACKGROUND

The N-terminal-pro-B natriuretic peptide (Nt-pro-BNP) is of diagnostic and prognostic value in coronary artery disease (CAD). We assessed the relationship between Nt-pro-BNP and (1) the extent of ischemia on stress myocardial perfusion imaging (MPI), and (2) changes between the basal and postexercise ejection fraction (EF), in stable patients with a normal EF.

METHODS AND RESULTS

One hundred and two patients with stable, documented CAD (EF, 62% +/- 8%) underwent an exercise-rest thallium-201 gated-MPI and serial Nt-pro-BNP assays. Myocardial perfusion imaging produced abnormal results in 57 patients (56%; group 1), and normal results in 45 patients (44%; group 2). Median baseline, immediate postexercise, and 3-hour postexercise Nt-pro-BNP values were higher in group 1 than in group 2: 182 vs 85, 201 vs 86, and 212 vs 99 pg/mL, respectively (P < .001 for all). Postexercise EF decreased in group 1 (53% +/- 11% vs 62% +/- 10%, P < .001), but not in group 2 (61% +/- 9% vs 62% +/- 7%, NS). The Nt-pro-BNP ruled out significant ischemia with a negative predictive value of 0.90, whereas patients within the higher tertile of Nt-pro-BNP had a fivefold higher risk of ischemia compared with patients within the lower tertile.

CONCLUSIONS

The post-stress increase in Nt-pro-BNP is related to myocardial ischemia and to postischemic left-ventricular dysfunction, and accurately predicts the presence or absence of myocardial perfusion defects.

The role of ethylenediamine tetraacetic acid (EDTA) as in vitro anticoagulant for diagnostic purposes

Anticoagulants are used to prevent clot formation both in vitro and in vivo. In the specific field of in vitro diagnostics, anticoagulants are commonly added to collection tubes either to maintain blood in the fluid state for hematological testing or to obtain suitable plasma for coagulation and clinical chemistry analyses. Unfortunately, no universal anticoagulant that could be used for evaluation of several laboratory parameters in a sample from a single test tube is available so far. Ethylenediamine tetraacetic acid (EDTA) is a polyprotic acid containing four carboxylic acid groups and two amine groups with lone-pair electrons that chelate calcium and several other metal ions. Calcium is necessary for a wide range of enzyme reactions of the coagulation cascade and its removal irreversibly prevents blood clotting within the collection tube. Historically, EDTA has been recommended as the anticoagulant of choice for hematological testing because it allows the best preservation of cellular components and morphology of blood cells. The remarkable expansion in laboratory test volume and complexity over recent decades has amplified the potential spectrum of applications for this anticoagulant, which can be used to stabilize blood for a variety of traditional and innovative tests. Specific data on the behavior of EDTA as an anticoagulant in hematology, including possible pitfalls, are presented. The use of EDTA for measuring cytokines, protein and peptides, and cardiac markers is described, with an outline of the protection of labile molecules provided by this anticoagulant. The use of EDTA in proteomics and in general clinical chemistry is also described in comparison with other anticoagulants and with serum samples. Finally, the possible uses of alternative anticoagulants instead of EDTA and the potential use of a universal anticoagulant are illustrated.

Brain natriuretic peptide: clinical and research challenges

Natriuretic peptides, in particular, brain or B-type, are useful for the assessment of patients presenting with dyspnea to the medical office or emergency department. Levels of natriuretic peptides are useful for assessing prognosis of heart failure or coronary syndrome patients. Less is known about serial peptide measurements for guiding treatment strategies in heart failure. The authors review the uses, pitfalls, and practical points for using natriuretic peptides clinically.

The relationship between N-terminal pro-brain natriuretic peptide and risk for hospitalization and mortality is curvilinear in patients with chronic heart failure

BACKGROUND

N-terminal pro-brain natriuretic peptide (NT-proBNP) carries prognostic information in patients with chronic heart failure and predicts risk for mortality and cardiovascular events. It is unknown whether NT-proBNP predicts risk for hospitalization for any cause. Furthermore, a clinically useful algorithm for risk stratification based on NT-proBNP as a continuous variable has not yet been described. We therefore evaluated NT-proBNP as a risk marker for mortality and hospitalization and developed a simple algorithm for risk stratification based on NT-proBNP as a continuous variable.

METHODS

Data from 345 patients with chronic heart failure were collected prospectively in our heart failure clinic, and the patients were followed for 28 months (median). Seventy patients died, and 201 patients were hospitalized. Cox proportional hazard models for mortality and hospitalization were constructed with NT-proBNP as a dichotomous (median 1381 pg/mL) and a continuous variable (log2 NT-proBNP).

RESULTS

Patients with supramedian levels of NT-proBNP had a 2.40-fold (95% CI 1.40-4.10) increased risk for mortality and 1.71-fold (95% CI 1.24-2.36) increased risk for hospitalization. The effect of doubling NT-proBNP on adjusted hazard ratios was 1.56 (95% CI 1.32-1.85) for mortality and 1.19 (95% CI 1.09-1.31) for hospitalization. We observed a curvilinear relationship between NT-proBNP and risk for mortality and hospitalization in the whole range of NT-proBNP.

CONCLUSIONS

N-terminal pro-brain natriuretic peptide predicts risk for hospitalization and mortality. A simple algorithm indicates that every time NT-proBNP is doubled, estimated hazard ratio for death increases by a factor of 1.56 (56%) and by a factor of 1.19 (19%) for hospitalization. Finally, the relationship between NT-proBNP and risk is curvilinear if NT-proBNP is considered as a continuous variable.

Measurement of Elecsys NT-proBNP in serum, K2 EDTA and heparin plasma

OBJECTIVE

There is controversial evidence on a matrix influence on the measurement of NT-proBNP.

DESIGN AND METHODS

We compared results of Elecsys NT-proBNP measurement on serum, K2 EDTA plasma and lithium heparin plasma.

RESULTS

Samples collected in K2 EDTA showed a marginally significant underestimation when compared to serum and heparin, whereas no significant difference was observed between serum and heparin plasma.

CONCLUSIONS

Serum, heparin and K2 EDTA plasma may be suitable for NT-proBNP measurement.

Transcoronary transplantation of functionally competent BMCs is associated with a decrease in natriuretic peptide serum levels and improved survival of patients with chronic postinfarction heart failure: results of the TOPCARE-CHD Registry

Although intracoronary administration of bone marrow-derived mononuclear progenitor cells (BMCs) may be associated with improved cardiac function in patients with chronic postinfarction heart failure, the impact on prognosis and clinical outcome of these patients is unknown. To identify potential predictors for a favorable clinical outcome, we assessed natriuretic peptide serum levels as objective markers of heart failure and the occurrence of cardiac death in relation to functional capacity of the infused cells in a consecutive series of 121 patients with chronic ischemic heart disease treated with intracoronary infusion of BMCs. Our analyses show that both N-terminal pro-brain natriuretic peptide (NT-proBNP) and N-terminal pro-atrial natriuretic peptide (NT-proANP) serum levels were significantly reduced in patients with established postinfarction heart failure 3 months after transcoronary progenitor cell administration. NT-proBNP serum levels greater than or equal to median (735 pg/mL) at baseline and a high number of infused progenitor cells with colony-forming capacity were the only independent predictors of a favorable response 3 months after intracoronary administration of BMCs. During extended clinical follow-up (577+/-442 days), a total of 14 deaths occurred in the overall patient population. Kaplan-Meier curves for both all cause and cardiac mortality showed that patients receiving a higher number of colony-forming cells were significantly less likely to die than those patients receiving low numbers of colony-forming cells (P=0.01). Most importantly, infusion of a high number of cells with colony-forming capacity was associated with a complete abrogation of increased mortality in patients with elevated NT-proBNP serum levels (> or =735 pg/mL; median) at baseline (P<0.001). Taken together, our results show that patients with objective evidence of postinfarction heart failure demonstrate a significant reduction of both NT-proBNP and NT-proANP serum levels within 3 months following intracoronary infusion of BMCs. Importantly, infusion of progenitor cells with a high functional capacity is associated with a significantly lower mortality during further follow-up.

N-terminal B-type natriuretic peptide concentrations are similarly increased by 30 minutes of moderate and brisk walking in patients with coronary artery disease

Elevated concentrations of B-type natriuretic peptide (BNP) and N-terminal pro- BNP (NT-proBNP) reflect elevated myocardial wall stress due to volume or pressure overload in cardiac disease. Recently, exercise-induced elevations of (NT-pro)BNP in coronary artery disease (CAD) patients have been reported to result from exercise-induced ischemia associated regional wall abnormalities. Therefore, the study aimed to examine NT-proBNP concentrations in patients with CAD after moderate and brisk walking (MW, BW). We hypothesized that BW induces higher increases than MW.

METHODS AND RESULTS

In randomized order 14 patients with stable CAD (12 male symbol/2 female symbol; 63 +/- 9 years; LV ejection fraction: 59+/-9%) of a out-patient rehabilitation group performed MW with 4.5 +/- 0.6 km/h (mean heart rate: 80 +/- 11/min) or BWat their allowed upper exercise heart rate of 102+/-9/min with a speed of 6.2 +/- 0.6 km/h for 30 min on a tartan track on two separate days. Blood samples were taken before, immediately, 1 h, 3 h and 1 day after exercise to determine NT-proBNP and cardiac troponin T (cTnT). Echocardiographic LV function was determined before and 1 h after exercise. Median concentrations of NT-proBNP significantly increased from 222 to 295 ng/l (MW) and from 222 to 296 ng/l (BW) without a difference between both modalities. cTnT remained below the detection limit of 0.01 microg/l. LV functions remained unchanged. A cutoff level of 250 ng/l distinguished CAD patients with elevated exercise-induced increases in NT-proBNP and a diminished LV ejection fraction at rest.

CONCLUSION

BW and MW induce similar increases in NT-proBNP in CAD patients without myocardial damage, which have to be considered when NT-proBNP is determined. Derived from the exercise- induced increase in NTproBNP, the myocardial strain in BW is not elevated in comparison to MW.

Unexplained week-to-week variation in BNP and NT-proBNP is low in chronic heart failure patients during steady state

BACKGROUND

The usefulness of brain-natriuretic-peptide (BNP) and N-terminal-pro-brain-natriuretic-peptide (NT-proBNP) for monitoring of chronic heart failure (CHF) patients has been questioned because of high levels of unexplained variation.

AIMS

Week-to-week total variance (CV(T)), unexplained variation (CV(I)), reference change values (RCV), index of individualities (IOI) and number of samples (N) with week-to-week intervals needed to estimate the underlying homeostatic set point (+/-15%) for BNP and NT-proBNP were calculated in pre-specified stable CHF patients.

METHODS AND RESULTS

We measured plasma concentrations of BNP and NT-proBNP, clinical and laboratory variables in 20 CHF patients with a 7-days interval. Only patients considered to be in steady state were included. The CV(I) was 15% (BNP) and 8% (NT-proBNP). CV(T) was 16% (BNP) and 8% (NT-proBNP) and RCV was 43% (BNP) and 23% (NT-proBNP). IOI was 0.14 for BNP and 0.03 for NT-proBNP and N was 1 for BNP and 1 for NT-proBNP.

CONCLUSIONS

Our data demonstrate that unexplained variation of BNP and NT-proBNP is low in CHF patients during steady state, which is a prerequisite for the use of these peptides for monitoring of the disease.

Biomarkers of cardiovascular damage

Acute coronary syndromes (ACS) are due to the rupture or erosion of atheromatous plaques. This produces, depending on plaque size, vascular anatomy and degree of collateral circulation, progressive tissue ischaemia which may progress to cardiomyocyte necrosis. This may then result in cardiac remodelling. Serum biomarkers are available which can be used for diagnosis of all of these stages. Markers to detect myocardial ischaemia at the pre-infarction stage are potentially the most interesting but also the most challenging. An ischaemia marker offers the opportunity to intervene to prevent progression to infarction. The problems with potential ischaemia markers are specificity and the reference diagnostic standard against which they can be judged. To date, only one, ischaemia-modified albumin(R), has reached the point where clinical studies can be performed. The measurement of the cardiac troponins, cardiac troponin T and cardiac troponin I, have become recognised as the diagnostic reference standard for myocardial necrosis. The sensitive nature of these tests has also revealed that myocardial necrosis is also found in a range of other clinical situations, highlighting the need to use all clinical information for diagnosis of acute myocardial infarction. The measurement of B-type natriuretic peptides can be shown to be diagnostic and prognostic in both ACS and detecting the sequelae of post-infarction myocardial insufficiency. The role of the B-type natriuretic peptides in detection of cardiac failure, both acute and chronic, is well defined but remains the subject of further studies, in ACS.

Increased plasma concentrations of N-terminal pro-B-type natriuretic peptide in patients with mild primary hyperparathyroidism

OBJECTIVE

Primary hyperparathyroidism (PHPT) is associated with heart disease. The aims of the present study were to evaluate how cardiac function and secretion of N-terminal pro-B-type natriuretic peptide (NT-proBNP) correlate in patients with mild PHPT, and how the plasma level of NT-proBNP is influenced by cure of the parathyroid disease.

DESIGN AND PATIENTS

Forty-two patients with PHPT without symptoms of heart disease were examined before and 1 year after curative parathyroidectomy.

MEASUREMENTS

Plasma or serum concentrations of NT-proBNP, calcium, PTH, creatinine, oestradiol, testosterone and SHBG were measured. Cardiac function was evaluated by equilibrium radionuclide angiography (ERNA).

RESULTS

At baseline, NT-proBNP levels correlated negatively with systolic function [left ventricular ejection fraction (LVEF), P < 0.001]. Twelve per cent of the patients had NT-proBNP levels above normal reference values preoperatively. One year postoperatively, the corresponding proportion was 21%. The mean plasma concentration of NT-proBNP increased after parathyroidectomy (P < 0.01) in parallel with a dip in diastolic function (peak filling rate, P < 0.05) and a falling trend in systolic function (LVEF, P = 0.08). The postoperative percentage changes in circulating NT-proBNP and total oestradiol correlated positively (P < 0.05).

CONCLUSIONS

Patients with mild PHPT and normal renal function may have high levels of circulating NT-proBNP despite the absence of symptomatic heart disease. Cure of the parathyroid disease is followed by a further increase in NT-proBNP secretion in parallel with ERNA measures, indicating subclinical changes in heart function. These results are in line with data indicating an association between PHPT and increased risk of premature death.

Head to head comparison of N-terminal pro-B-type natriuretic peptide and B-type natriuretic peptide in patients with/without left ventricular systolic dysfunction

BACKGROUND

Human pro-B-type natriuretic peptide is cleaved into the active B-type natriuretic peptide (BNP) and the inactive fragment NT-proBNP. It is unclear if, similar to BNP, NT-proBNP can be used as a marker of impaired left ventricular (LV) ejection fraction (EF). This study evaluated the analytical performance of both assays to detect LV systolic dysfunction.

METHODS

In 72 patients with various degrees of left ventricular systolic dysfunction (LVSD), blood analysis for BNP and NT-proBNP was performed prior to cardiac catheterization, using a point-of-care analyzer (Biosite) and a fully automated laboratory analyzer (Roche-Elecsys), respectively. The within-run and between-run imprecision for BNP and NT-proBNP was calculated.

RESULTS

Both markers were able to detect impaired LV EF with the largest area under the receiver-operating-characteristic curve for NT-proBNP (NT-proBNP: 0.851 (0.747-0.924); BNP: 0.803 (0.692-0.887) 95% confidence interval; P = 0.07). A significant correlation was observed between BNP and NT-proBNP (r = 0.9; P < 0.0001). Estimating the within-run imprecision, the coefficient of variance for BNP was 3.14% (n = 20, mean 316 ng/L) to 3.32% (n = 20, mean 820 ng/L) and for NT-proBNP 0.9% (n = 20, mean 4390.8 ng/L) to 1.4% (n = 20, mean 225 ng/L). The between-run imprecision for NT-proBNP ranged between 2.1% (n = 20, mean 224.6 ng/L) and 2% (n = 20, mean 4391 ng/L). Optimal discriminator values for BNP and NT-proBNP were 139 ng/L and 358 ng/L, respectively. However, adjusting the BNP cut-off value to 54 ng/L improved the negative predictive value and sensitivity of the assay.

CONCLUSION

Similar to BNP, NT-proBNP is a promising marker in identifying LVSD. Although both assays are reliable and have good analytical performance, their diagnostic cut-off value is dynamic and population-dependent. The slightly wider detection range and the more stable structure of NT-proBNP compared to the BNP assay suggest that NT-proBNP could play an additional role in the evaluation of patients with LV systolic dysfunction.

N-Terminal pro-brain natriuretic peptide: normal ranges in the pediatric population including method comparison and interlaboratory variability

The aim of the present study was the investigation of N-terminal pro-brain natriuretic peptide (NT-proBNP) in the pediatric population. This is essential for adequate monitoring and classification of pediatric patients with heart disease, but no consistent data are available yet. In addition, the comparability of two commercially available NT-proBNP assays and the inter-laboratory variability for the most suitable one were assessed. For this purpose, 408 subjects (1-29 years) were included. NT-proBNP was determined with a non-competitive electrochemiluminescent immunoassay (Roche NT-proBNP; n = 402) and a competitive enzyme-immunoassay (Biomedica NT-proBNP; n = 402). Inter-laboratory variability was evaluated for the Roche assay by stepwise inclusion of four and 11 centers throughout Germany, respectively. Roche NT-proBNP ranged from 5.0 to 391.5 ng/L, with higher values for younger children. The 97.5th (75th) percentile curve ranged from 319.9 ng/L (231.2 ng/L, 1-3 years) to 114.9 ng/L (53.3 ng/L, 18 years). In contrast, Biomedica NT-proBNP ranged from 253.7 to 7602.8 ng/L, with no significant age dependency. The mean difference between the assays was 1649.7 ng/L (95% confidence interval 1546.3-1753.1 ng/L). Inter-laboratory variability ranged from 6.5% to 3.8%, covering a range from 51.3 to 6618.1 ng/L. The assay seems to influence the interpretation of resulting NT-proBNP values and therefore has to be chosen carefully. For the monitoring and classification of pediatric patients with congenital heart disease, age-based NT-proBNP values should be used.