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.

Electrophoresis Titration Model of a Moving Redox Boundary Chip for a Point-of-Care Test of an Enzyme-Linked Immunosorbent Assay

Enzyme-linked immunosorbent assays (ELISAs) have been widely used in clinical examination, food safety, and environmental analyses. However, they still face a great challenge in designing a device for a point-of-care test (POCT) due to its bulk optical detector and complexity. Herein an electrophoresis titration (ET) model of a moving redox boundary (MRB) was proposed for constructing an ET-ELISA chip of a POCT just with sextuplet electrode pairs and laminated cells. The chip had an anodic well, middle well, and cathode well which were connected by microchannels. The ELISA process was conducted in the bottom of the middle well, where horseradish peroxidase (HRP) catalyzed 3,3',5,5'-tetra-methyl benzidine (TMB) as a blue TMB dimer with two positive charges. Under an electrical field of 29 V, the TMB dimer migrated into the titration channel and reacted with the ascorbic acid, creating an MRB. The MRB motion was a function of antigen content, indicating a visual distance-based assay. As a proof of concept, a C-reactive protein was chosen as a model antigen. The experiments systemically validated the ET-ELISA model and method. Particularly, the chip was smartphone-detected, traditional power supply free, and did not use sulfuric acid used in typical ELISA, making the ET-ELISA method extremely simple, portable, and safe. The ET-ELISA has great potential to visual and portable ELISA in clinical medicine, the environment, and food safety immunoassay.

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

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

Cardiac Troponin I and Amino-Terminal Pro B-Type Natriuretic Peptide in Dogs With Stable Chronic Kidney Disease

Background

Increased concentrations of N‐terminal pro B‐type natriuretic peptide (NT‐proBNP) and cardiac troponin I (cTnI) in dogs with azotemia have been documented. Knowledge of mechanisms behind increased concentrations of cardiac biomarkers in dogs with azotemia is warranted for correct interpretation of test results.

Objectives

The aim of the article was to investigate possible associations between plasma concentrations of cTnI and NT‐proBNP, respectively, and patient characteristics, glomerular filtration rate (GFR), a plasma volume factor (PVF) derived from scintigraphic examination (PVf), systolic blood pressure (SBP), selected hematologic and biochemical variables, and echocardiographic measurements in dogs with stable chronic kidney disease (CKD) and in healthy dogs.

Animals

Fifty student‐, staff‐, and client‐owned dogs were included. Twenty‐three of the dogs were healthy and 27 were diagnosed with CKD.

Methods

In this cross‐sectional observational study, dogs with a previous diagnosis of CKD and healthy control dogs were included. At inclusion, all dogs were characterized by physical examination, repeated blood pressure measurements, complete urinalysis, hematology and biochemistry panel, echocardiography, abdominal ultrasound examination of the entire urinary tract, and scintigraphic examination for measurement of GFR.

Results

Plasma volume factor and PCV were independently associated with NT‐proBNP (Radj2 = 0.42; P < .0001). Age, body weight (BW), and SBP were independently associated with cTnI (Radj2 = 0.50; P < .0001).

Conclusions and Clinical Importance

Neither NT‐proBNP nor cTnI concentrations were independently associated with measured GFR. Thus, findings were not suggestive of passive accumulation of either marker, suggesting that increased circulating concentrations of cTnI and NT‐proBNP can be interpreted similarly in dogs with stable CKD as in dogs without CKD.

Point-of-Care Testing

This article provides an overview of the current use of point-of-care testing (POCT) and its utility for patients’ self-management of chronic disease states. Pharmacists utilize POCT to provide rapid laboratory diagnostic results as a monitoring tool in the management of their patients and in order to improve medication outcomes. Considerations for the transition to use of POCT in the home to further improve disease management and improve health care cost-effectiveness are discussed. Devices available for home use include those suitable for management of diabetes mellitus, hypertension, congestive heart failure, and anticoagulation. Many of these devices include software capabilities enabling patients to share important health information with health care providers using a computer. Limitations and challenges surrounding implementation of home POCT for patients include reliability of instrumentation, ability to coordinate data collection, necessary training requirements, and cost-effectiveness. Looking forward, the successful integration of POCT into the homes of patients is contingent on a concerted effort made by all members of the health care team.

Recent advances in point-of-care testing for natriuretic peptides: potential impact on heart failure diagnosis and management

Heart failure is a leading cause of morbidity and mortality worldwide. The presenting symptoms of heart failure are often nonspecific. The diagnosis of heart failure has traditionally relied heavily upon clinical exam findings, which are often subjective and have low sensitivity. Efficient and rapid diagnosis of heart failure in the emergency room setting can reduce health care costs, hospital admission and ER visits, and improve patient care. Natriuretic peptides are objective biomarkers that can help with diagnosis, prognosis and management of heart failure. The most extensively studied and clinically utilized natriuretic peptides include brain natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP). Point-of-care testing in the emergency room setting can result in faster triage times. Point-of-care testing can also be utilized in the outpatient setting for real-time management of patients with heart failure.

State of the art of immunoassay methods for B-type natriuretic peptides: An update

The aim of this review article is to give an update on the state of the art of the immunoassay methods for the measurement of B-type natriuretic peptide (BNP) and its related peptides. Using chromatographic procedures, several studies reported an increasing number of circulating peptides related to BNP in human plasma of patients with heart failure. These peptides may have reduced or even no biological activity. Furthermore, other studies have suggested that, using immunoassays that are considered specific for BNP, the precursor of the peptide hormone, proBNP, constitutes a major portion of the peptide measured in plasma of patients with heart failure. Because BNP immunoassay methods show large (up to 50%) systematic differences in values, the use of identical decision values for all immunoassay methods, as suggested by the most recent international guidelines, seems unreasonable. Since proBNP significantly cross-reacts with all commercial immunoassay methods considered specific for BNP, manufacturers should test and clearly declare the degree of cross-reactivity of glycosylated and non-glycosylated proBNP in their BNP immunoassay methods. Clinicians should take into account that there are large systematic differences between methods when they compare results from different laboratories that use different BNP immunoassays. On the other hand, clinical laboratories should take part in external quality assessment (EQA) programs to evaluate the bias of their method in comparison to other BNP methods. Finally, the authors believe that the development of more specific methods for the active peptide, BNP1-32, should reduce the systematic differences between methods and result in better harmonization of results.