A Gray Zone Assigned to Inconclusive Results of Quantitative Diagnostic Tests: Application to the Use of Brain Natriuretic Peptide for Diagnosis of Heart Failure in Acute Dyspneic Patients

Comparison of Differences in Cohort (Forward) and Case Control (Backward) Methodologic Approaches for Validation of the Hypotension Prediction Index

BACKGROUND

The Hypotension Prediction Index (the index) software is a machine learning algorithm that detects physiologic changes that may lead to hypotension. The original validation used a case control (backward) analysis that has been suggested to be biased. This study therefore conducted a cohort (forward) analysis and compared this to the original validation technique.

METHODS

A retrospective analysis of data from previously reported studies was conducted. All data were analyzed identically with two different methodologies, and receiver operating characteristic curves were constructed. Both backward and forward analyses were performed to examine differences in area under the receiver operating characteristic curves for the Hypotension Prediction Index and other hemodynamic variables to predict a mean arterial pressure (MAP) less than 65 mmHg for at least 1 min 5, 10, and 15 min in advance.

RESULTS

The analysis included 2,022 patients, yielding 4,152,124 measurements taken at 20-s intervals. The area under the curve for the index predicting hypotension analyzed by backward and forward methodologies respectively was 0.957 (95% CI, 0.947 to 0.964) versus 0.923 (95% CI, 0.912 to 0.933) 5 min in advance, 0.933 (95% CI, 0.924 to 0.942) versus 0.923 (95% CI, 0.911 to 0.933) 10 min in advance, and 0.929 (95% CI, 0.918 to 0.938) versus 0.926 (95% CI, 0.914 to 0.937) 15 min in advance. No variable other than MAP had an area under the curve greater than 0.7. The areas under the curve using forward analysis for MAP predicting hypotension 5, 10, and 15 min in advance were 0.932 (95% CI, 0.920 to 0.940), 0.929 (95% CI, 0.918 to 0.938), and 0.932 (95% CI, 0.921 to 0.940), respectively. The R2 for the variation in the index due to MAP was 0.77.

CONCLUSIONS

Using an updated methodology, the study found that the utility of the Hypotension Prediction Index to predict future hypotensive events is high, with an area under the receiver operating characteristics curve similar to that of the original validation method.

EDITOR’S PERSPECTIVE

Missing values and inconclusive results in diagnostic studies - A scoping review of methods

Most diagnostic studies exclude missing values and inconclusive results from the analysis or apply simple methods resulting in biased accuracy estimates. This may be due to the lack of availability or awareness of appropriate methods. This scoping review aimed to provide an overview of strategies to handle missing values and inconclusive results in the reference standard or index test in diagnostic accuracy studies. Conducting a systematic literature search in MEDLINE, Cochrane Library, and Web of Science, we could identify many articles proposing methods for addressing missing values in the reference standard. There are also several articles describing methods regarding missing values or inconclusive results in the index test. The latter encompass imputation, frequentist and Bayesian likelihood, model-based, and latent class methods. While methods for missing values in the reference standard are regularly applied in practice, this is not true for methods addressing missing values and inconclusive results in the index test. Our comprehensive overview and description of available methods may raise further awareness of these methods and will enhance their application. Future research is needed to compare the performance of these methods under different conditions to give valid and robust recommendations for their usage in various diagnostic accuracy research scenarios.

Test-retest variability of plasma biomarkers in Alzheimer's disease and its effects on clinical prediction models

INTRODUCTION

The effect of random error on the performance of blood-based biomarkers for Alzheimer's disease (AD) must be determined before clinical implementation.

METHODS

We measured test-retest variability of plasma amyloid beta (Aβ)42/Aβ40, neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and phosphorylated tau (p-tau)217 and simulated effects of this variability on biomarker performance when predicting either cerebrospinal fluid (CSF) Aβ status or conversion to AD dementia in 399 non-demented participants with cognitive symptoms.

RESULTS

Clinical performance was highest when combining all biomarkers. Among single-biomarkers, p-tau217 performed best. Test-retest variability ranged from 4.1% (Aβ42/Aβ40) to 25% (GFAP). This variability reduced the performance of the biomarkers (≈ΔAUC [area under the curve] -1% to -4%) with the least effects on models with p-tau217. The percent of individuals with unstable predicted outcomes was lowest for the multi-biomarker combination (14%).

DISCUSSION

Clinical prediction models combining plasma biomarkers-particularly p-tau217-exhibit high performance and are less effected by random error. Individuals with unstable predicted outcomes ("gray zone") should be recommended for further tests.

Robustness of CSF Aβ42/40 and Aβ42/P-tau181 measured using fully automated immunoassays to detect AD-related outcomes

INTRODUCTION

This study investigated the comparability of cerebrospinal fluid (CSF) cutoffs for Elecsys immunoassays for amyloid beta (Aβ)42/Aβ40 or Aβ42/phosphorylated tau (p-tau)181 and the effects of measurement variability when predicting Alzheimer's disease (AD)-related outcomes (i.e., Aβ-positron emission tomography [PET] visual read and AD neuropathology).

METHODS

We studied 750 participants (BioFINDER study, Alzheimer's Disease Neuroimaging Initiative [ADNI], and University of California San Francisco [UCSF]). Youden's index was used to identify cutoffs and to calculate accuracy (Aβ-PET visual read as outcome). Using longitudinal variability in Aβ-negative controls, we identified a gray zone around cut-points where the risk of an inconsistent predicted outcome was >5%.

RESULTS

For Aβ42/Aβ40, cutoffs across cohorts were <0.059 (BioFINDER), <0.057 (ADNI), and <0.058 (UCSF). For Aβ42/p-tau181, cutoffs were <41.90 (BioFINDER), <39.20 (ADNI), and <46.02 (UCSF). Accuracy was ≈90% for both Aβ42/Aβ40 and Aβ42/p-tau181 using these cutoffs. Using Aβ-PET as an outcome, 8.7% of participants fell within a gray zone interval for Aβ42/Aβ40, compared to 4.5% for Aβ42/p-tau181. Similar findings were observed using a measure of overall AD neuropathologic change (7.7% vs. 3.3%). In a subset with CSF and plasma Aβ42/40, the number of individuals within the gray zone was ≈1.5 to 3 times greater when using plasma Aβ42/40.

DISCUSSION

CSF Aβ42/p-tau181 was more robust to the effects of measurement variability, suggesting that it may be the preferred Elecsys-based measure in clinical practice and trials.

The impact of grey zones on the accuracy of agreement measures for ordinal tables

Background

In an inter-rater agreement study, if two raters tend to rate considering different aspects of the subject of interest or have different experience levels, a grey zone occurs among the levels of a square contingency table showing the inter-rater agreement. These grey zones distort the degree of agreement between raters and negatively impact the decisions based on the inter-rater agreement tables. In this sense, it is important to know how the existence of a grey zone impacts the inter-rater agreement coefficients to choose the most reliable agreement coefficient against the grey zones to reach out with more reliable decisions.

Methods

In this article, we propose two approaches to create grey zones in simulations setting and conduct an extensive Monte Carlo simulation study to figure out the impact of having grey zones on the weighted inter-rater agreement measures for ordinal tables over a comprehensive simulation space.

Results

The weighted inter-rater agreement coefficients are not reliable against the existence of grey zones. Increasing sample size and the number of categories in the agreement table decreases the accuracy of weighted inter-rater agreement measures when there is a grey zone. When the degree of agreement between the raters is high, the agreement measures are not significantly impacted by the existence of grey zones. However, if there is a medium to low degree of inter-rater agreement, all the weighted coefficients are more or less impacted.

Conclusions

It is observed in this study that the existence of grey zones has a significant negative impact on the accuracy of agreement measures especially for a low degree of true agreement and high sample and tables sizes. In general, Gwet’s AC2 and Brennan-Prediger’s κ with quadratic or ordinal weights are reliable against the grey zones.

Supplementary Information

The online version contains supplementary material available at (10.1186/s12874-021-01248-3).

Impact of the Prevalence of Cognitive Impairment on the Accuracy of the Montreal Cognitive Assessment: The Advantage of Using two MoCA Thresholds to Identify Error-prone Test Scores

OBJECTIVES

The focus of this study is the classification accuracy of the Montreal Cognitive Assessment (MoCA) for the detection of cognitive impairment (CI). Classification accuracy can be low when the prevalence of CI is either high or low in a clinical sample. A more robust result can be expected when avoiding the range of test scores within which most classification errors are expected, with adequate predictive values for more clinical settings.

METHODS

The classification methods have been applied to the MoCA data of 5019 patients in the Uniform Data Set of the University of Washington's National Alzheimer's Coordinating Center, to which 30 Alzheimer Disease Centers (ADCs) contributed.

RESULTS

The ADCs show sample prevalence of CI varying from 0.22 to 0.87. Applying an optimal cutoff score of 23, the MoCA showed for only 3 of 30 ADCs both a positive predictive value (PPV) and a negative predictive value (NPV) ≥0.8, and in 18 cases, a PPV ≥0.8 and for 13 an NPV ≥0.8. Overall, the test scores between 22 and 25 have low odds of true against false decisions of 1.14 and contains 55.3% of all errors when applying the optimal dichotomous cut-point. Excluding the range 22 to 25 offers higher classification accuracies for the samples of the individual ADCs. Sixteen of 30 ADCs showed both NPV and PPV ≥0.8, 25 show a PPV ≥0.8, and 21 show an NPV ≥0.8.

CONCLUSION

In comparison to a dichotomous threshold, considering the most error-prone test scores as uncertain enables a classification that offers adequate classification accuracies in a larger number of clinical settings.

Ultrasonographic inferior vena cava diameter response to trauma resuscitation after 1 hour predicts 24-hour fluid requirement

BACKGROUND

Identification of occult hypovolemia in trauma patients is difficult. We hypothesized that in acute trauma patients, the response of ultrasound-measured minimum inferior vena cava diameter (IVCDMIN), IVC Collapsibility Index (IVCCI), minimum internal jugular diameter (IJVDMIN) or IJV Collapsibility Index (IJVCI) after up to 1 hour of fluid resuscitation would predict 24-hour resuscitation intravenous fluid requirements (24FR).

METHODS

An NTI-funded, American Association for the Surgery of Trauma Multi-Institutional Trials Committee prospective, cohort trial was conducted at four Level I Trauma Centers. Major trauma patients were screened for an IVCD of 12 mm or less or IVCCI of 50% or less on initial focused assessment sonographic evaluations for trauma. A second IVCD was obtained 40 minutes to 60 minutes later, after standard-of-care fluid resuscitation. Patients whose second measured IVCD was less than 10 mm were deemed nonrepleted (NONREPLETED), those 10 mm or greater were repleted (REPLETED). Prehospital and initial resuscitation fluids and 24FR were recorded. Demographics, Injury Severity Score, arterial blood gasses, length of stay, interventions, and complications were recorded. Means were compared by ANOVA and categorical variables were compared via χ. Receiver operating characteristic curves analysis was used to compare the measures as 24FR predictors.

RESULTS

There were 4,798 patients screened, 196 were identified with admission IVCD of 12 mm or IVCCI of 50% or less, 144 were enrolled. There were 86 REPLETED and 58 NONREPLETED. Demographics, initial hemodynamics, or laboratory measures were not significantly different. NONREPLETED had smaller IVCD (6.0 ± 3.7 mm vs. 14.2 ± 4.3 mm, p < 0.001) and higher IVCCI (41.7% ± 30.0% vs. 13.2% ± 12.7%, p < 0.001) but no significant difference in IJVD or IJVCCI. REPLETED had greater 24FR than NONREPLETED (2503 ± 1751 mL vs. 1,243 ± 1,130 mL, p = 0.003). Receiver operating characteristic analysis indicates IVCDMIN predicted 24FR (area under the curve [AUC], 0.74; 95% confidence interval [CI], 0.64-0.84; p < 0.001) as did IVCCI (AUC, 0.75; 95% CI, 0.65-0.85; p < 0.001) but not IJVDMIN (AUC, 0.48; 95% CI, 0.24-0.60; p = 0.747) or IJVCI (AUC, 0.54; 95% CI, 0.42-0.67; p = 0.591).

CONCLUSION

Ultrasound assessed IVCDMIN and IVCCI response initial resuscitation predicts 24-hour fluid resuscitation requirements.

LEVEL OF EVIDENCE

Diagnostic tests or criteria, level II.

Comparison of the Diagnostic Accuracy of Plasma N-Terminal Pro-Brain Natriuretic Peptide in Patients <80 to those >80 Years of Age with Heart Failure

Plasma N-Terminal Pro-Brain Natriuretic Peptide (NTproBNP) is known to increase with age, however, the performance of this biomaker is unclear in patients >80. This study sought to define the diagnostic accuracy of plasma NTproBNP in patients >80 in a large unselected population of heart failure (HF) patients admitted to a Tertiary Hospital in the United Kingdom. 1,995 consecutive patients over a 12 month period were screened for HF through our NTproBNP led HF service. 413 patients had their first presentation of HF and 36.1% of these patients were >80. There was a reduction in accuracy of NTproBNP with age according to the area under the curve, with an area under the curve for all HF patients of 0.734 and a 7.5% reduction in receiver operating characteristic curve area for patients >80 years compared with those under 60 to 79 years of age. The lowest NTproBNP recorded for patients with HF >80 years of age was 466 pg/ml. In HF patients >80, 40.6% patients were diagnosed with HFrEF, 31.1% with HFpEF and 28.2% with HFmrEF. Overall NTproBNP is less accurate at identifying HF in patients >80 years of age and the lowest NTproBNP recorded for a HF patient was 466 pg/ml suggesting that the NTproBNP threshold for ruling out HF in patients >80 years of age should be modified.

The Clinical Relevance of Methods for Handling Inconclusive Medical Test Results: Quantification of Uncertainty in Medical Decision-Making and Screening

BACKGROUND

although the existence of inconclusive medical test results or bio-markers is widely recognized, there are indications that this inherent diagnostic uncertainty is sometimes ignored. This paper discusses three methods for defining and determining inconclusive medical test results, which use different definitions and differ in clinical relevance.

METHODS

the TG-ROC (two graphs receiver operating characteristics) method is the easiest to use, while the grey zone method and the uncertain interval method require more extensive calculations.

RESULTS

this paper discusses the technical details of the methods, as well as advantages and disadvantages for their clinical use. TG-ROC and the grey zone method can help in the acquisition of high rates of diagnostic certainty, but can exclude large groups. The uncertain interval method can prevent decisions that are the most uncertain, invalid and unreliable, while excluding smaller groups.

CONCLUSIONS

the identification of uncertain test scores is relevant, because these scores indicate the need to obtain better information or to await further developments. The methods presented help to determine inconclusive test scores and can help to reduce erroneous decisions. However, further research and development is desirable.

Mini-fluid Challenge of 100 ml of Crystalloid Predicts Fluid Responsiveness in the Operating Room

BACKGROUND

Mini-fluid challenge of 100 ml colloids is thought to predict the effects of larger amounts of fluid (500 ml) in intensive care units. This study sought to determine whether a low quantity of crystalloid (50 and 100 ml) could predict the effects of 250 ml crystalloid in mechanically ventilated patients in the operating room.

METHODS

A total of 44 mechanically ventilated patients undergoing neurosurgery were included. Volume expansion (250 ml saline 0.9%) was given to maximize cardiac output during surgery. Stroke volume index (monitored using pulse contour analysis) and pulse pressure variations were recorded before and after 50 ml infusion (given for 1 min), after another 50 ml infusion (given for 1 min), and finally after 150 ml infusion (total = 250 ml). Changes in stroke volume index induced by 50, 100, and 250 ml were recorded. Positive fluid challenges were defined as an increase in stroke volume index of 10% or more from baseline after 250 ml.

RESULTS

A total of 88 fluid challenges were performed (32% of positive fluid challenges). Changes in stroke volume index induced by 100 ml greater than 6% (gray zone between 4 and 7%, including 19% of patients) predicted fluid responsiveness with a sensitivity of 93% (95% CI, 77 to 99%) and a specificity of 85% (95% CI, 73 to 93%). The area under the receiver operating curve of changes in stroke volume index induced by 100 ml was 0.95 (95% CI, 0.90 to 0.99) and was higher than those of changes in stroke volume index induced by 50 ml (0.83 [95% CI, 0.75 to 0.92]; P = 0.01) and pulse pressure variations (0.65 [95% CI, 0.53 to 0.78]; P < 0.005).

CONCLUSIONS

Changes in stroke volume index induced by rapid infusion of 100 ml crystalloid predicted the effects of 250 ml crystalloid in patients ventilated mechanically in the operating room.

Interval of Uncertainty: An Alternative Approach for the Determination of Decision Thresholds, with an Illustrative Application for the Prediction of Prostate Cancer

Often, for medical decisions based on test scores, a single decision threshold is determined and the test results are dichotomized into positive and negative diagnoses. It is therefore important to identify the decision threshold with the least number of misclassifications. The proposed method uses trichotomization: it defines an Uncertain Interval around the point of intersection between the two distributions of individuals with and without the targeted disease. In this Uncertain Interval the diagnoses are intermixed and the numbers of correct and incorrect diagnoses are (almost) equal. This Uncertain Interval is considered to be a range of test scores that is inconclusive and does not warrant a decision. It is expected that defining such an interval with some precision, prevents a relatively large number of false decisions, and therefore results in an increased accuracy or correct classifications rate (CCR) for the test scores outside this Uncertain Interval. Clinical data and simulation results confirm this. The results show that the CCR is systematically higher outside the Uncertain Interval when compared to the CCR of the decision threshold based on the maximized Youden index. For strong tests with a very small overlap between the two distributions, it can be difficult to determine an Uncertain Interval. In simulations, the comparison with an existing method for test-score trichotomization, the Two-graph Receiver Operating Characteristic (TG-ROC), showed smaller differences between the two distributions for the Uncertain Interval than for TG-ROC's Intermediate Range and consequently a more improved CCR outside the Uncertain Interval. The main conclusion is that the Uncertain Interval method offers two advantages: 1. Identification of patients for whom the test results are inconclusive; 2. A higher estimated rate of correct decisions for the remaining patients.

[Usefulness of natriuretic peptide testing and Doppler echocardiography at bedside in the diagnosis of acute heart failure]

Acute heart failure is a common condition that leads to hospital admission, with important mortality and readmission rates. A prompt and accurate diagnosis of this condition by hospitalists is essential for an early and tailored medical management. The use of natriuretic peptide testing (BNP and NT-proBNP) through a two cut-point strategy is currently recommended as the first-line diagnostic complement to the initial clinical evaluation in the acute care setting. Transthoracic Doppler echocardiography is an other noninvasive method that can be used at bedside, especially in patients with intermediate, inconclusive natriuretic peptides levels. In this regard, left ventricular ejection fraction and several simple Doppler indexes (restrictive mitral filling pattern, spectral tissue Doppler E/e' ratio), have been validated in the emergency diagnosis of acute heart failure. The aim of the present review is to overview the respective contribution of natriuretic peptides and Doppler echocardiography at bedside to the diagnosis of acute heart failure in the acute care setting.

Diagnosing Acute Heart Failure in the Emergency Department: A Systematic Review and Meta-analysis

BACKGROUND

Acute heart failure (AHF) is one of the most common diagnoses assigned to emergency department (ED) patients who are hospitalized. Despite its high prevalence in the emergency setting, the diagnosis of AHF in ED patients with undifferentiated dyspnea can be challenging.

OBJECTIVES

The primary objective of this study was to perform a systematic review and meta-analysis of the operating characteristics of diagnostic elements available to the emergency physician for diagnosing AHF. Secondary objectives were to develop a test-treatment threshold model and to calculate interval likelihood ratios (LRs) for natriuretic peptides (NPs) by pooling patient-level results.

METHODS

PubMed, EMBASE, and selected bibliographies were searched from January 1965 to March 2015 using MeSH terms to address the ability of the following index tests to predict AHF as a cause of dyspnea in adult patients in the ED: history and physical examination, electrocardiogram, chest radiograph (CXR), B-type natriuretic peptide (BNP), N-terminal proB-type natriuretic peptide (NT-proBNP), lung ultrasound (US), bedside echocardiography, and bioimpedance. A diagnosis of AHF based on clinical data combined with objective test results served as the criterion standard diagnosis. Data were analyzed using Meta-DiSc software. Authors of all NP studies were contacted to obtain patient-level data. The Quality Assessment Tool for Diagnostic Accuracy Studies-2 (QUADAS-2) for systematic reviews was utilized to evaluate the quality and applicability of the studies included.

RESULTS

Based on the included studies, the prevalence of AHF ranged from 29% to 79%. Index tests with pooled positive LRs ≥ 4 were the auscultation of S3 on physical examination (4.0, 95% confidence interval [CI] = 2.7 to 5.9), pulmonary edema on both CXR (4.8, 95% CI = 3.6 to 6.4) and lung US (7.4, 95% CI = 4.2 to 12.8), and reduced ejection fraction observed on bedside echocardiogram (4.1, 95% CI = 2.4 to 7.2). Tests with low negative LRs were BNP < 100 pg/mL (0.11, 95% CI = 0.07 to 0.16), NT-proBNP < 300 pg/mL (0.09, 95% CI = 0.03 to 0.34), and B-line pattern on lung US LR (0.16, 95% CI = 0.05 to 0.51). Interval LRs of BNP concentrations at the low end of "positive" results as defined by a cutoff of 100 pg/mL were substantially lower (100 to 200 pg/mL; 0.29, 95% CI = 0.23 to 0.38) than those associated with higher BNP concentrations (1000 to 1500 pg/mL; 7.12, 95% CI = 4.53 to 11.18). The interval LR of NT-proBNP concentrations even at very high values (30,000 to 200,000 pg/mL) was 3.30 (95% CI = 2.05 to 5.31).

CONCLUSIONS

Bedside lung US and echocardiography appear to the most useful tests for affirming the presence of AHF while NPs are valuable in excluding the diagnosis.

The role of uncertainty regarding the results of screening immunoassays in blood establishments

The risk of uncertain results in infectious agents' tests is recognized in blood establishments, being particularly evident during the blood donor selection. The current risk-based approaches require risk assessment and "risk-based thinking". Accordingly, the blood establishment should consider the effect of uncertainty in all the technical decisions taken in a screening laboratory. Since the post-transfusion safety is one of the blood establishments' goals, the risk of post-transfusion infection should be evaluated and actions taken to decrease the chance of blood donations validation use false negative results. This article reviews and discusses the sources of uncertainty of infectious agents' reported results in blood establishments. It describes a set of sources of uncertainty that should be considered in screening immunoassay's decisions. The infectious agents' uncertainty concern is critical for reporting reliable results.

Clinical relevance of pulse pressure variations for predicting fluid responsiveness in mechanically ventilated intensive care unit patients: the grey zone approach

Introduction

Pulse pressure variation (PPV) has been shown to predict fluid responsiveness in ventilated intensive care unit (ICU) patients. The present study was aimed at assessing the diagnostic accuracy of PPV for prediction of fluid responsiveness by using the grey zone approach in a large population.

Methods

The study pooled data of 556 patients from nine French ICUs. Hemodynamic (PPV, central venous pressure (CVP) and cardiac output) and ventilator variables were recorded. Responders were defined as patients increasing their stroke volume more than or equal to 15% after fluid challenge. The receiver operating characteristic (ROC) curve and grey zone were defined for PPV. The grey zone was evaluated according to the risk of fluid infusion in hypoxemic patients.

Results

Fluid challenge led to increased stroke volume more than or equal to 15% in 267 patients (48%). The areas under the ROC curve of PPV and CVP were 0.73 (95% confidence interval (CI): 0.68 to 0.77) and 0.64 (95% CI 0.59 to 0.70), respectively (P <0.001). A grey zone of 4 to 17% (62% of patients) was found for PPV. A tidal volume more than or equal to 8 ml.kg⁻¹ and a driving pressure (plateau pressure - PEEP) more than 20 cmH₂O significantly improved the area under the ROC curve for PPV. When taking into account the risk of fluid infusion, the grey zone for PPV was 2 to 13%.

Conclusions

In ventilated ICU patients, PPV values between 4 and 17%, encountered in 62% patients exhibiting validity prerequisites, did not predict fluid responsiveness.

Estimation of diagnostic test accuracy without full verification: a review of latent class methods

The performance of a diagnostic test is best evaluated against a reference test that is without error. For many diseases, this is not possible, and an imperfect reference test must be used. However, diagnostic accuracy estimates may be biased if inaccurately verified status is used as the truth. Statistical models have been developed to handle this situation by treating disease as a latent variable. In this paper, we conduct a systematized review of statistical methods using latent class models for estimating test accuracy and disease prevalence in the absence of complete verification.

Radiographic heart size and its rate of increase as tests for onset of congestive heart failure in Cavalier King Charles Spaniels with mitral valve regurgitation

BACKGROUND

In canine mitral regurgitation (MR) the rate of heart enlargement increases in the last year before congestive heart failure (CHF). Measurement of heart size and its rate of increase may be useful tests for CHF in MR.

OBJECTIVES

To determine the value of vertebral heart scale (VHS) and its rate of increase (∆VHS units/month) for diagnosing the presence and predicting the onset of CHF.

ANIMALS

Longitudinal study of 94 Cavalier King Charles Spaniels (CKCS).

METHODS

VHS was measured at intervals before CHF. ∆VHS/month was calculated from sequential pairs of VHS measurements and the interval between them. Diagnostic accuracy and utility were determined by the areas under receiver operating characteristic plots (AUROC), and likelihood ratios (LR).

RESULTS

AUROC for VHS at the onset of CHF was 0.93 (95% CI, 0.96-0.90), to predict CHF 1-12 months before CHF was 0.74 (95% CI, 0.81-0.66), and for ∆VHS/month at CHF was 0.98 (95% CI, 0.99-0.96). Interval LRs and their cutoff values for CHF were for VHS: 13 (95% CI, 20-7.3) at ≥12.7; 1.2 (95% CI, 2.0-0.68) between 12.7 and 12.0; 0.04 (95% CI, 0.18-0.01) at ≤12.0, and for ∆VHS/month: 15 (95% CI, 30-7.7) at ≥0.08; 0.72 (95% CI, 2.0-0.25) between 0.08 and 0.06; and 0.05 (95% CI, 0.13-0.02) at ≤0.06.

CONCLUSIONS AND CLINICAL IMPORTANCE

Under the conditions of this study, VHS and particularly ∆VHS/month are useful measurements for detecting onset of CHF in CKCS with MR.

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.

Cardiac ultrasound helps for differentiating the causes of acute dyspnea with available B-type natriuretic peptide tests

INTRODUCTION

The aim of this study was to evaluate the role of cardiac ultrasound in diagnosing acute heart failure (AHF) in patients with acute dyspnea with available plasma B-type natriuretic peptide (BNP) level.

METHODS

Patients with acute dyspnea presenting to the emergency department (ED) of a tertiary medical center were prospectively enrolled. The enrolled 84 patients received both BNP tests and cardiac ultrasound studies and were classified into AHF and non-heart failure groups.

RESULTS

Plasma BNP levels were higher in the AHF group (1236 ± 1123 vs 354 ± 410 pg/mL; P < .001). The AHF group had larger left ventricular end-diastolic dimension (LVEDD; 32 ± 7 vs 27 ± 4 mm/m(2); P < .001) and worse left ventricular ejection fraction (52% ± 18% vs 64% ± 15%; P = .003). Multiple logistic regression analysis showed that both BNP levels more than 100 pg/mL and LVEDD were independent predictors for AHF. In patients with plasma BNP levels within gray zone of 100 to 500 pg/mL, LVEDD was larger in the AHF group than that in the non-heart failure group (29 ± 4 vs 26 ± 4 mm/m(2); P = .044).

CONCLUSION

Both LVEDD by cardiac ultrasound and BNP levels can help emergency physicians independently diagnose AHF in the ED. In patients with plasma BNP levels within 100 to 500 pg/mL, cardiac ultrasound can help differentiate heart failure or not.

Natriuretic peptides in the diagnosis and management of chronic heart failure

Circulating levels of the BNP system can help in the diagnosis of cardiovascular disease and provide prognostic information not only for patients who have HF but also for the general population and other patient groups. Changes over time also carry prognostic information, and studies are assessing BNP-guided treatment strategies. With the identification of circulating molecular forms of BNP, new insights regarding the biology of the BNP system are emerging that may improve the diagnostic and prognostic value of BNP. Likewise, accounting for rs198389 (a common single nucleotide polymorphism that increases BNP levels) may help to further refine the use of components of the BNP system as biomarkers.

Natriuretic peptides and echocardiography in acute dyspnoea: implication of elevated levels with normal systolic function

AIMS

Previous evaluations of natriuretic peptide (NP) levels in patients with acute dyspnoea presenting to the emergency department (ED) have selected only a minority of patients for echocardiography. We aimed to evaluate the association between NPs and more subtle echocardiographic findings and to assess the potential for NPs to provide additional prognostic information beyond that provided by echocardiography in 'all-comers' with acute dyspnoea.

METHODS AND RESULTS

Prospective echocardiograms were performed on 338/412 patients presenting to the ED with acute dyspnoea. B-type natriuretic peptide and NT-proBNP were measured on presentation. Patients were followed-up for 1 year. Decompensated heart failure was diagnosed in 37% of patients and 13% died. The diagnostic accuracy (c-statistic) of BNP and NT-proBNP for identifying LVEF <or= 40% was 0.88 (P < 0.001) and 0.86 (P < 0.001), respectively. The c-statistics for BNP and NT-proBNP for identifying diastolic dysfunction were 0.67 (P < 0.001) and 0.67 (P < 0.001); but only 0.57 (P = 0.09) and 0.60 (P = 0.02) in patients with LVEF >or= 50%. Natriuretic peptides, but not LV mass or diastolic parameters, independently predicted mortality at 1 year in all patients and in those with an LVEF >or= 50%.

CONCLUSION

In an acute dyspnoea population with 'all-comers' undergoing echocardiography, NPs correlate strongly with structural abnormalities and identify those with preserved LVEF at highest risk for death. Careful interpretation of elevated NP values is needed in the presence of preserved systolic function.

Lack of diagnostic and prognostic utility of circulating plasma myeloperoxidase concentrations in patients presenting with dyspnea

BACKGROUND

Plasma myeloperoxidase (MPO), an inflammatory biomarker, is associated with increased mortality in patients with acute coronary syndrome or chronic left ventricular systolic dysfunction. We sought to assess the diagnostic accuracy of MPO for acute decompensated heart failure (ADHF) and its prognostic value for patients with acute dyspnea.

METHODS

In a prospective, observational study conducted in 5 US centers, 412 patients [mean (SD) age, 58 (14) years; 39% women] presenting with dyspnea to the emergency department were enrolled and followed for 1 year. Clinical, serum/plasma biomarker [MPO, B-type natriuretic peptide (BNP), N-terminal proBNP (NT-proBNP)], and transthoracic echocardiographic data were obtained.

RESULTS

We observed no differences in MPO concentration (P = 0.07) between patients with ADHF [n = 147; median, 553 pmol/L; interquartile range (IQR), 415-738 pmol/L] and those without ADHF (n = 265; median, 576 pmol/L; IQR, 413-884 pmol/L). The diagnostic accuracy for ADHF was excellent for BNP [area under the ROC curve (AUC), 0.90; P < 0.001] and NT-proBNP (AUC, 0.90; P < 0.001) but poor for MPO (AUC, 0.46; P = 0.18). MPO appeared uncorrelated with echocardiographic measures of cardiac structure or function. The observed 1-year mortality rate was 12%. MPO concentration also appeared unrelated to mortality [hazard ratio, 1.25 (above vs below the median); 95% CI, 0.71-2.18], whereas BNP (P = 0.001) and NT-proBNP (P < 0.001) were significant predictors of mortality. MPO concentration provided no prognostic information in addition to that of BNP or NT-proBNP concentration.

CONCLUSIONS

Unlike natriuretic peptides, MPO concentration was not predictive of ADHF diagnosis or 1-year mortality in a heterogeneous sample of emergency department patients with acute dyspnea.

Differential diagnosis of acute dyspnea: the value of B natriuretic peptides in the emergency department

Congestive heart failure (CHF) is the main cause of acute dyspnea in patients presenting to an emergency department (ED) and is associated with high morbidity and mortality. B-type natriuretic peptide (BNP) is a polypeptide, released by ventricular myocytes in direct proportion to wall tension, which lowers renin-angiotensin-aldosterone activation. For the diagnosis of CHF, both BNP and the biologically inactive NT-proBNP have similar accuracy. Threshold values are higher in an elderly population, and in patients with renal dysfunction. They might also have a prognostic value. Studies have demonstrated that the use of BNP or NT-proBNP in dyspneic patients early following admission to the ED, reduced the time to discharge and total treatment cost. BNP and NT-proBNP should be available in every ED 24 h a day, because the literature strongly suggests the beneficial impact of an early appropriate diagnosis and treatment in dyspneic patients. The purpose of this review is to indicate recent developments in biomarkers of heart failure and to evaluate their impact on clinical use in the emergency setting.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Amino-terminal pro-B-type natriuretic peptide: 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.

Current clinical applications of spectral tissue Doppler echocardiography (E/E' ratio) as a noninvasive surrogate for left ventricular diastolic pressures in the diagnosis of heart failure with preserved left ventricular systolic function

Congestive heart failure with preserved left ventricular systolic function has emerged as a growing epidemic medical syndrome in developed countries, which is characterized by high morbidity and mortality rates. Rapid and accurate diagnosis of this condition is essential for optimizing the therapeutic management. The diagnosis of congestive heart failure is challenging in patients presenting without obvious left ventricular systolic dysfunction and additional diagnostic information is most commonly required in this setting. Comprehensive Doppler echocardiography is the single most useful diagnostic test recommended by the ESC and ACC/AHA guidelines for assessing left ventricular ejection fraction and cardiac abnormalities in patients with suspected congestive heart failure, and non-invasively determined basal or exercise-induced pulmonary capillary hypertension is likely to become a hallmark of congestive heart failure in symptomatic patients with preserved left ventricular systolic function. The present review will focus on the current clinical applications of spectral tissue Doppler echocardiography used as a reliable noninvasive surrogate for left ventricular diastolic pressures at rest as well as during exercise in the diagnosis of heart failure with preserved left ventricular systolic function. Chronic congestive heart failure, a disease of exercise, and acute heart failure syndromes are characterized by specific pathophysiologic and diagnostic issues, and these two clinical presentations will be discussed separately.