Comparing serum and pleural fluid pro-brain natriuretic peptide (NT-proBNP) levels with pleural-to-serum albumin gradient for the identification of cardiac effusions misclassified by Light's criteria

ERS statement on benign pleural effusions in adults

The incidence of non-malignant pleural effusions far outweighs that of malignant pleural effusions and is estimated to be at least 3-fold higher. These so-called benign effusions do not follow a "benign course" in many cases, with mortality rates matching and sometimes exceeding those of malignant pleural effusions. In addition to the impact on patients, healthcare systems are also significantly affected, with recent US epidemiological data demonstrating that 75% of resource allocation for pleural effusion management is spent on non-malignant pleural effusions (excluding empyema). Despite this significant burden of disease, and by existing at the junction of multiple medical specialties, reflecting a heterogenous constellation of medical conditions, non-malignant pleural effusions are rarely the focus of research or the subject of management guidelines. With this European Respiratory Society Task Force, we assembled a multispecialty collaborative across 11 countries and three continents to provide a statement based on systematic searches of the medical literature to highlight evidence in the management of the following clinical areas: a diagnostic approach to transudative effusions, heart failure, hepatic hydrothorax, end-stage renal failure, benign asbestos-related pleural effusion, post-surgical effusion and nonspecific pleuritis.

Pleural effusion guidelines from ICS and NCCP Section 1: Basic principles, laboratory tests and pleural procedures

Pleural effusion is a common problem in our country, and most of these patients need invasive tests as they can't be evaluated by blood tests alone. The simplest of them is diagnostic pleural aspiration, and diagnostic techniques such as medical thoracoscopy are being performed more frequently than ever before. However, most physicians in India treat pleural effusion empirically, leading to delays in diagnosis, misdiagnosis and complications from wrong treatments. This situation must change, and the adoption of evidence-based protocols is urgently needed. Furthermore, the spectrum of pleural disease in India is different from that in the West, and yet Western guidelines and algorithms are used by Indian physicians. Therefore, India-specific consensus guidelines are needed. To fulfil this need, the Indian Chest Society and the National College of Chest Physicians; the premier societies for pulmonary physicians came together to create this National guideline. This document aims to provide evidence based recommendations on basic principles, initial assessment, diagnostic modalities and management of pleural effusions.

Age affects the diagnostic accuracy of serum N-terminal pro-B-type natriuretic peptide for heart failure in patients with pleural effusion

BACKGROUND

Serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a well-recognized diagnostic marker for heart failure (HF) in patients with dyspnea or pleural effusion (PE). The effects of age on the diagnostic accuracy of NT-proBNP in dyspneic patients are widely known; however, whether its diagnostic accuracy is affected by age in patients with PE remains unknown. This study aimed to investigate the influence of age on the diagnostic accuracy of serum NT-proBNP for HF in patients with PE.

METHODS

Patients with PE were recruited from the BUFF (Biomarkers for patients with Undiagnosed pleural eFFusion) cohort and the SIMPLE (a Study Investigating Markers in PLeural Effusion) cohort. Serum NT-proBNP on admission and final diagnosis were extracted from the participant's medical records. The diagnostic accuracy of serum NT-proBNP was evaluated by a operating characteristic (ROC) curve analysis. The influence of age on the diagnostic accuracy of NT-proBNP was investigated through subgroup analyses.

RESULTS

One hundred and four participants were enrolled from the BUFF cohorts (HF, 32; non-HF, 72). One hundred and sixteen participants were enrolled from the SIMPLE cohort (HF, 21; non-HF, 95). The area under the ROC curve (AUCs) of NT-proBNP in the pooled cohort was 0.78 (95 %CI: 0.71 - 0.85). The AUC of NT-proBNP decreased in older patients.

CONCLUSION

Serum NT-proBNP has moderate diagnostic accuracy for HF in old patients with PE. The diagnostic accuracy of serum NT-proBNP in these patients decreases with the advancement of age.

The laboratory investigation of pleural fluids: An update based on the available evidence

Selecting appropriate laboratory tests based on available evidence is central to improve clinical effectiveness and impacting on patient outcome. Although long studied, there is no mutual agreement upon pleural fluid (PF) management in the laboratory context. Given the experienced confusion about the real contribution of laboratory investigations to guide clinical interpretation, in this update, we tried to identify useful tests for the PF analysis, aiming to unravel critical points and to define a common line in requesting modalities and practical management. We performed a careful literature review and a deepened study on available guidelines to finalize an evidence-based test selection, intended for clinicians' use to streamline PF management. The following tests depicted the basic PF profile routinely needed: (1) abbreviated Light's criteria (PF/serum total protein ratio and PF/serum lactate dehydrogenase ratio) and (2) cell count with differential analysis of haematological cells. This profile fulfils the primary goal to determine the PF nature and discriminate between exudative and transudative effusions. In specific circumstances, clinicians may consider additional tests as follows: the albumin serum to PF gradient, which reduces exudate misclassification rate by Light's criteria in patients with cardiac failure assuming diuretics; PF triglycerides, in differentiating chylothorax from pseudochylothorax; PF glucose, for identification of parapneumonic effusions and other causes of effusion, such as rheumatoid arthritis and malignancy; PF pH, in suspected infectious pleuritis and to give indications for pleural drainage; and PF adenosine deaminase, for a rapid detection of tuberculous effusion.

Pleural fluid biochemical analysis: the past, present and future

Identifying the cause of pleural effusion is challenging for pulmonologists. Imaging, biopsy, microbiology and biochemical analyses are routinely used for diagnosing pleural effusion. Among these diagnostic tools, biochemical analyses are promising because they have the advantages of low cost, minimal invasiveness, observer independence and short turn-around time. Here, we reviewed the past, present and future of pleural fluid biochemical analysis. We reviewed the history of Light’s criteria and its modifications and the current status of biomarkers for heart failure, malignant pleural effusion, tuberculosis pleural effusion and parapneumonic pleural effusion. In addition, we anticipate the future of pleural fluid biochemical analysis, including the utility of machine learning, molecular diagnosis and high-throughput technologies. Clinical Chemistry and Laboratory Medicine (CCLM) should address the topic of pleural fluid biochemical analysis in the future to promote specific knowledge in the laboratory professional community.

Diagnostics in Pleural Disease

Pleural disease diagnostics represent a sprawling topic that has enjoyed a renaissance in recent years from humble beginnings. Whilst pleural patients are heterogeneous as a population and in the aetiology of the disease with which they present, we provide an overview of the typical diagnostic approach. Pleural fluid analysis is the cornerstone of the diagnostic pathway; however, it has many shortcomings. Strong cases have been made for more invasive upfront investigations, including image-guided biopsies or local anaesthetic thoracoscopy, in selected populations. Imaging can guide the diagnostic process as well as act as a vehicle to facilitate therapies, and this is never truer than with the recent advances in thoracic ultrasound.

A Predictive Model for the Identification of Cardiac Effusions Misclassified by Light's Criteria

OBJECTIVES

The application of Light's criteria misidentifies approximately 30% of transudates as exudates, particularly in patients on diuretics with cardiac effusions. The purpose of this study was to establish a predictive model to effectively identify cardiac effusions misclassified by Light's criteria.

METHODS

We retrospectively studied 675 consecutive patients with pleural effusion diagnosed by Light's criteria as exudates, of which 43 were heart failure patients. A multivariate logistic model was developed to predict cardiac effusions. The performance of the predictive model was assessed by receiver operating characteristic (ROC) curves, as well as by examining the calibration.

RESULTS

It was found that protein gradient of >23 g/L, pleural fluid lactate dehydrogenase (PF-LDH) levels, ratio of pleural fluid LDH to serum LDH level (P/S LDH), pleural fluid adenosine deaminase (PF-ADA) levels, and N-terminal pro-brain natriuretic peptide (NT-pro-BNP) levels had a significant impact on the identification of cardiac effusions, and those were simultaneously analyzed by multivariate regression analysis. The area under the curve (AUC) value of the model was 0.953. The model also had higher discriminatory properties than protein gradients (AUC, 0.760) and NT-pro-BNP (AUC, 0.906), all at a P value of <.01.

CONCLUSION

In cases of suspected cardiac effusion, or where clinicians cannot identify the cause of an exudative effusion, this model may assist in the correct identification of exudative effusions as cardiac effusions.

Pleural effusions in acute decompensated heart failure: Prevalence and prognostic implications

BACKGROUND

The incidence of pleural effusions (PEs) in acute decompensated heart failure (ADHF) is not well established. We aimed to determine their prevalence, clinical characteristics and prognostic implications.

METHODS

Retrospective review of 3245 consecutive patients with ADHF from the Spanish RICA Registry. The clinical characteristics of those with or without PEs on chest radiographs were compared and a predictive PE model was generated.

RESULTS

Patient's median age was 80 years and 60% had a left ventricular ejection fraction (LVEF) >50%. PEs were seen in 46% of the cases, and their distribution was as follows: 58% bilateral, 27% right-sided and 14% left-sided. Male gender (OR 2.18; 95%CI 1.23-3.87), serum amino-terminal fraction of the pro-brain natriuretic peptide (NT-pro-BNP) levels >3500 pg/ml (OR 2.2; 95%CI 1.25-3.77), estimated systolic pulmonary artery pressure (sPAP) >55 mm Hg by echocardiography (OR 2.05; 95%CI 1.12-3.75), and serum prealbumin <15 mg/l (OR 1.96; 95%CI 1.08-3.52) were associated with PE development in a multivariate analysis. Serum NT-proBNP >8000 pg/ml, and systolic arterial pressure <110 mm Hg, but not PEs, independently predicted overall 1-year mortality.

CONCLUSIONS

PEs are present on chest radiographs in nearly half of ADHF patients. They are mainly bilateral or right-sided and predominate in males with elevated sPAP on echocardiography and high serum levels of NT-proBNP. PEs do not independently predict 1-year mortality.

Development and validation of a scoring system for the identification of pleural exudates of cardiac origin

BACKGROUND

Light's criteria misclassify about 30% of cardiac effusions as exudates, possibly leading to unnecessary testing. Our purpose was to derive and validate a scoring model to effectively identify these falsely categorized cardiac effusions, in the setting of natriuretic peptide lacking data.

METHODS

We retrospectively analyzed data from 3182 patients with exudative pleural effusions based on Light's criteria, of whom 276 had heart failure (derivation set). A scoring model was generated with those variables identified as independent predictors of cardiac effusions in a logistic regression analysis, and further evaluated in an independent population of 1165 patients.

RESULTS

The score consisted of age ≥75years (3 points), albumin gradient >1.2g/dL (3 points), pleural fluid lactate dehydrogenase <250U/L (2 points), bilateral effusions on chest radiograph (2 points), and protein gradient >2.5g/dL (1 point). At the best cutoff of ≥7 points, the score yielded 92% diagnostic accuracy, a likelihood ratio positive of 12.7 and a likelihood ratio negative of 0.39 for labeling cardiac effusions in the derivation sample. The respective figures in the validation sample were 87%, 6.5 and 0.33. Notably, the score had higher discriminatory properties than protein and albumin gradients in both the derivation (respective area under the curve - AUC - of 0.925, 0.825, and 0.801) and validation (respective AUC of 0.908 0.862 and 0.802; all p≤0.01) cohorts.

CONCLUSIONS

A simple scoring system can assist clinicians in accurately identifying false cardiac exudates when natriuretic peptides are not available.

Unilateral Pleural Effusions with More Than One Apparent Etiology. A Prospective Observational Study

RATIONALE

Evaluation of a pleural effusion has historically focused on establishing a single etiology. Pleural fluid may accumulate through multiple pathophysiological processes. The prevalence of multiple causes for pleural effusions has not been established. The identification of contributing processes may improve clinical outcomes.

OBJECTIVES

The objective of this prospectively collected case series was to establish the prevalence and nature of multiple etiologies for a unilateral pleural effusion.

METHODS

Consecutive patients presenting with an undiagnosed unilateral pleural effusion were recruited at a tertiary pleural center. Patients underwent a comprehensive structured diagnostic clinical evaluation and were followed up for a minimum of 12 months, after which one or more diagnoses were recorded independently by two experienced clinicians.

MEASUREMENTS AND MAIN RESULTS

One hundred thirty patients were recruited to the study over a 24-month period, and 126 patients completed follow up. Altogether, 88 patients (70%) had a single cause for their pleural effusion, and 38 (30%) had multiple causes. Serum N-terminal pro-brain natriuretic peptide (NT-pro BNP) greater than or equal to 1,500 pg/ml was predictive of multiple etiologies. NT-pro BNP had a sensitivity and specificity of 79 and 88%, respectively, for establishing heart failure as a primary or contributory cause. Thirteen patients with a malignant pleural effusion also had an NT-pro BNP greater than or equal to 1,500 pg/ml.

CONCLUSIONS

This study is the first to estimate the prevalence of more than one identifiable cause for a unilateral pleural effusion. Out of 130 study subjects, 38 (30%) had multiple causes for an effusion. The identification of multiple pathologies underlying an accumulation of fluid in the pleural space may be important in determining optimum treatment and improving patients' symptoms.

Pleural diseases

PURPOSE OF REVIEW

Due to the increasing burden of pleural diseases worldwide, a personalized cost-effective management of these conditions is essential to optimize the healthcare sources. The current review is focused on latest evidence in diagnostic work-up and management of pleural diseases.

RECENT FINDINGS

Recent research highlights the increasing role of thoracic ultrasound in both diagnostic and therapeutic interventions and the potential suitability of cytological sampling from pleural effusions for molecular analysis, essential requirement for a satisfactory test in the era of personalized anticancer therapy. The thoracoscopic approach, by means of rigid or semirigid instruments, remains the gold standard, and attractive tools to increase diagnostic yield in semirigid pleuroscopy include insulated-tip diathermic knife and cryprobe. Talc pleurodesis and indwelling pleural catheters are the most effective interventions, and their combination, likely to result in additional benefits, is currently under investigation.

SUMMARY

Because of the huge variety of possible clinical settings, a proper management of pleural diseases should be tailored on a case-by-case basis and requires a multidisciplinary approach. Recent advances in technologies has conferred to interventional pulmonology an increasing relevant role in this context, leading to the development of a dedicated subspecialty, and training programs are urgently needed to standardize skills and care pathways.

The past, current and future of diagnosis and management of pleural disease

Pleural disease is frequently encountered by the chest physician. Pleural effusions arise as the sequelae of underlying disease processes including pressure/volume imbalances, infection and malignancy. In addition to pleural effusions, persistent air leaks after surgery and bronchopleural fistulae remain a challenge. Our understanding of pleural disease including its diagnosis and management, have made tremendous strides. The introduction of the molecular detection of organism specific infection, risk stratification and improvements in the non-surgical treatment of patients with pleural infection are all within reach and may be the standard of care in the very near future. Malignant pleural effusion management continues to evolve with the introduction of tunneled pleural catheters and procedures combining that and chemical pleurodesis. These advances in the diagnostic and therapeutic evaluation of pleural disease as well as what seems to be an increasing multidisciplinary interest in the space foretell a bright future.

Diagnostic Accuracy of Natriuretic Peptides for Heart Failure in Patients with Pleural Effusion: A Systematic Review and Updated Meta-Analysis

Background

Previous studies have reported that natriuretic peptides in the blood and pleural fluid (PF) are effective diagnostic markers for heart failure (HF). These natriuretic peptides include N-terminal pro-brain natriuretic peptide (NT-proBNP), brain natriuretic peptide (BNP), and midregion pro-atrial natriuretic peptide (MR-proANP). This systematic review and meta-analysis evaluates the diagnostic accuracy of blood and PF natriuretic peptides for HF in patients with pleural effusion.

Methods

PubMed and EMBASE databases were searched to identify articles published in English that investigated the diagnostic accuracy of BNP, NT-proBNP, and MR-proANP for HF. The last search was performed on 9 October 2014. The quality of the eligible studies was assessed using the revised Quality Assessment of Diagnostic Accuracy Studies tool. The diagnostic performance characteristics (sensitivity, specificity, and other measures of accuracy) were pooled and examined using a bivariate model.

Results

In total, 14 studies were included in the meta-analysis, including 12 studies reporting the diagnostic accuracy of PF NT-proBNP and 4 studies evaluating blood NT-proBNP. The summary estimates of PF NT-proBNP for HF had a diagnostic sensitivity of 0.94 (95% confidence interval [CI]: 0.90–0.96), specificity of 0.91 (95% CI: 0.86–0.95), positive likelihood ratio of 10.9 (95% CI: 6.4–18.6), negative likelihood ratio of 0.07 (95% CI: 0.04–0.12), and diagnostic odds ratio of 157 (95% CI: 57–430). The overall sensitivity of blood NT-proBNP for diagnosis of HF was 0.92 (95% CI: 0.86–0.95), with a specificity of 0.88 (95% CI: 0.77–0.94), positive likelihood ratio of 7.8 (95% CI: 3.7–16.3), negative likelihood ratio of 0.10 (95% CI: 0.06–0.16), and diagnostic odds ratio of 81 (95% CI: 27–241). The diagnostic accuracy of PF MR-proANP and blood and PF BNP was not analyzed due to the small number of related studies.

Conclusions

BNP, NT-proBNP, and MR-proANP, either in blood or PF, are effective tools for diagnosis of HF. Additional studies are needed to rigorously evaluate the diagnostic accuracy of PF and blood MR-proANP and BNP for the diagnosis of HF.

Relationship Between Prohormone Brain Natriuretic Peptide (NT-proBNP) Level and Severity of Pulmonary Dysfunction in Patients With Chronic Congestive Heart Failure

Introduction: Congestive heart failure (CHF) is a common disease and its prevalence is increasing in industrialized countries. NT-proBNP measurement is an established diagnostic test for diagnosis of CHF in patients who present to emergency room with acute dyspnea. The primary object of this study was to determine the relationship between levels of brain natriuretic peptide precursor and severity of lung function impairment in patients with chronic CHF.

Methods: This cross-sectional and analytical study that performed in Tuberculosis and Lung Disease Research Center of Tabriz University of Medical Sciences on 95 patients with chronic heart failure, and relation between NT-proBNP levels and pulmonary function parameters were examined.

Results: Sixty-four patients were male and 31 were female. The average age of male and females was 62.90 ± 11.54 and 61.61 ± 11.98 years, respectively. A significant inverse linear correlation was found between NT-proBNP and FEV1 (P < 0.001, r = -0.367), FVC (P < 0.001, r = -0.444), TLC (P = 0.022, r = -0.238), maximal midexpiratory flow (MMEF) (P = 0.047, r = -0.207) and left ventricular ejection fraction (LVEF) (P < 0.001, r = -0.461). A significant positive linear correlation was found between NT-proBNP and FEV1/FVC (P = 0.013, r = 0.257), RV/TLC (P = 0.003, r=0.303) and 5 Hz Raw (r = 0.231, P = 0.024).

Conclusion: This study showed that, both restrictive and obstructive ventilator impairments can occur in chronic CHF and as NT-proBNP increases appropriate to hemodynamic deterioration, pulmonary dysfunction increases.

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

Background and Objective

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

Methods

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

Results

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

Conclusions

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

Identifying transudates misclassified by Light's criteria

PURPOSE OF REVIEW

Light's criteria combine three dichotomous tests into a decision rule that is considered positive if any one of the tests is positive. This strategy clearly maximizes sensitivity, although at the expense of specificity. Although Light's criteria identify 98% of pleural exudates, they misclassify about 25% of transudates as exudates. The way to overcome this limitation is discussed in this review.

RECENT FINDINGS

Traditionally, measurement of the protein gradient between the serum and pleural fluid has been recommended to decrease the misclassification rate of Light's criteria. A recent study demonstrated that a gradient between the albumin levels in the serum and the pleural fluid more than 1.2 g/dl performs significantly better than a protein gradient more than 3.1 g/dl to correctly categorize mislabeled cardiac effusions (83 vs. 55%). On the other hand, the accuracy of a pleural fluid to serum albumin ratio less than 0.6 excelled when compared with albumin and protein gradients in patients with miscategorized hepatic hydrothoraces (77 vs. 62 vs. 61%).

SUMMARY

The simplest strategy to reveal the true transudative nature of heart failure-related effusions, labeled as exudates by Light's criteria, is to calculate the serum to pleural fluid albumin gradient. Conversely, for misclassified hepatic hydrothoraces, measurement of the pleural to serum albumin ratio is recommended. The serum to pleural fluid protein gradient should no longer be considered the preferred test for this purpose.

Comparison of pleural N-terminal pro-B-type natriuretic peptide, midregion pro-atrial natriuretic peptide and mid-region pro-adrenomedullin for the diagnosis of pleural effusions associated with cardiac failure

BACKGROUND AND OBJECTIVE

The purpose of this study was to compare the diagnostic utility of pleural fluid N-terminal pro-B-type natriuretic peptide (NT-proBNP), midregion pro-atrial natriuretic peptide (MR-proANP) and midregion pro-adrenomedullin (MR-proADM) for discriminating heart failure (HF)-associated effusions.

METHODS

NT-proBNP, MR-proANP and MR-proADM were measured by commercially available methodologies in the pleural fluid of a retrospective cohort of 185 consecutive patients with pleural effusions, of whom 95 had acute decompensated HF. Receiver-operating characteristic and area under the curve (AUC) analyses allowed comparisons of the discriminative properties of these biomarkers to be made at their optimal cut-off points.

RESULTS

The diagnostic accuracy of NT-proBNP and MR-proANP for HF as quantified by the AUC was 0.935 and 0.918, respectively, whereas MR-proADM was of limited value (AUC = 0.62). A pleural fluid MR-proANP >260 pmol/L or NT-proBNP >1700 pg/mL argues for HF (likelihood ratio (LR) positive >5), while levels below these cut-off values significantly decrease the probability of having the disease (respective LR negative 0.19 and 0.10). The optimal cut-off points for natriuretic peptides were influenced by age, renal function and body mass index. Finally, both NT-proBNP and the albumin gradient correctly identified more than 80% of those cardiac effusions misclassified as exudates by standard criteria.

CONCLUSIONS

MR-proANP is as valuable a diagnostic tool as NT-proBNP for diagnosing or excluding HF as the cause of pleural effusion.

Assessment of circulating N-terminal pro B-type natriuretic peptide concentration to differentiate between cardiac from noncardiac causes of pleural effusion in cats

OBJECTIVE

To determine the diagnostic ability of blood N-terminal pro B-type natriuretic peptide (NT-proBNP) measurement to differentiate between congestive heart failure (CHF) and noncardiogenic causes for moderate to severe pleural effusion in cats.

DESIGN

Prospective observational study.

SETTING

University teaching hospital.

ANIMALS

Twenty-one cats with moderate to severe pleural effusion.

INTERVENTIONS

Venous blood sampling for NT-proBNP measurement.

MEASUREMENT AND RESULTS

According to the results of echocardiographic examination, cats were classified in a group with CHF (n = 11) or noncongestive heart failure (N-CHF, n = 10). NT-proBNP was measured via a feline-specific test in EDTA plasma with protease inhibitor. NT-proBNP was significantly (P < 0.0001) higher in the CHF group ( median 982 pmol/L, 355-1,286 pmol/L) than in the N-CHF group (median 69 pmol/L, 26 - 160 pmol/L) and discriminated exactly (area under the curve = 1.0, 95% confidence interval 1.0-1.0) between both groups. Optimum cut-off value considering all samples was 258 pmol/L.

CONCLUSION

In this small population of cats with pleural effusion, NT-proBNP was able to differentiate between cats with cardiogenic and noncardiogenic causes of effusion. With the currently recommended method of measurement (ie, EDTA plasma with protease inhibitor), a cut-off value of 258 pmol/L discriminates effectively between cats with and without CHF.

Pleural fluid biomarkers: beyond the Light criteria

Although distinguishing transudates from exudates through the Light criteria is still considered a pragmatic first step in the diagnostic work-up of pleural effusions, the measurement of various pleural fluid biomarkers may aid in the identification of common and specific entities, such as heart failure (natriuretic peptides), tuberculosis (adenosine deaminase), malignancy (mesothelin, fibulin-3, immunocytochemical stains), or bacterial pleural infections (C-reactive protein). The use of these biomarkers is currently encouraged as a routine diagnostic procedure.

Metabonomic classification and detection of small molecule biomarkers of malignant pleural effusions

To date, most research has been focused on the benign molecules in pleural effusions, and diagnosis of malignant ones still remains challenging. In the present study, targeting the small molecules as potential biomarkers to predict the malignancy of the effusions, the metabolic profiles of 81 clinical pleural effusions (41 malignant effusions from lung cancer and 40 benign ones) were investigated through a NMR-based metabonomic approach. In (1)H NMR analysis, a total of ten small molecules in the effusions were simultaneously determined. Significantly higher mean values of valine, lactate, and alanine and markedly lower signal intensities of acetoacetate, trimethylamine-N-oxide, and α- and β-glucose were observed in malignant pleural effusions compared with those in benign ones. DFA modeling of NMR spectra subjected to a validation allowed the malignant effusions to be discriminated from benign ones in both training and validation groups. Currently, the conventional clinical analyses on chemical constituents in effusions could not provide a reliable prediction of malignancy of the effusions; the present results revealed that the small molecules might serve as useful biomarkers for diagnosis of the effusions, and the present NMR-based metabonomic approach provided a valuable potential to rapidly and sensitively predict the malignancy of the pleural effusions.

Pleural fluid analysis: standstill or a work in progress?

Pleural fluid analysis yields important diagnostic information in pleural effusions in combination with clinical history, examination, and radiology. For more than 30 years, the initial and most pragmatic step in this process is to determine whether the fluid is a transudate or an exudate. Light's criteria remain the most robust in separating the transudate-exudate classification which dictates further investigations or management. Recent studies have led to the evaluation and implementation of a number of additional fluid analyses that may improve the diagnostic utility of this method. This paper discusses the current practice and future direction of pleural fluid analysis in determining the aetiology of a pleural effusion. While this has been performed for a few decades, a number of other pleural characteristics are becoming available suggesting that this diagnostic tool is indeed a work in progress.

Utilization of B-type natriuretic peptide and NT-proBNP in the diagnosis of pleural effusions due to heart failure

PURPOSE OF REVIEW

The natriuretic peptides B-type natriuretic peptide (BNP) and NT-proBNP have been incorporated into the existing clinical guidelines for the diagnostic evaluation of heart failure. Recent evidence has provided important information regarding the relative value of each of these peptides to differentiate between pleural effusions caused by heart failure and those attributable to other causes.

RECENT FINDINGS

In a meta-analysis of 10 studies, which included 1120 patients, pleural fluid levels of NT-proBNP had a pooled sensitivity and specificity of 94%, a positive likelihood ratio of 15.2, and a negative likelihood ratio of 0.06 in identifying heart failure-related effusions. Because pleural fluid and serum natriuretic peptide levels are closely correlated and display similar discriminatory properties, blood tests alone are sufficient. More than 85% of heart failure patients whose pleural fluids meet exudative criteria exhibit high pleural NT-proBNP concentrations. The diagnostic performance of pleural fluid BNP has been reported to be inferior to that of NT-proBNP.

SUMMARY

NT-proBNP is an established biomarker of heart failure-associated effusions and the most effective tool for recognizing cardiac effusions that are misclassified as exudates by Light's criteria. If clinicians choose pleural fluid specimens for natriuretic peptide testing, the lower diagnostic accuracy of BNP makes it a poor substitute for NT-proBNP measurements.

Diagnostic value of pleural effusion ischaemia-modified albumin in patients with cardiac failure

Background

Ischaemia-modified albumin (IMA) is a relatively new marker of ischaemia. IMA has not been studied previously in pleural effusions due to congestive heart failure (CHF). The aim of our study was to assess the diagnostic value of IMA in the pleural fluid (PF) and serum for the identification of pleural effusion due to CHF.

Methods

The concentrations of pleural fluid and serum IMA were measured in a total of 40 patients: 10 with CHF and 30 with non-cardiac failure (10 with acute pulmonary embolism, 10 with parapneumonic effusion and 10 with malignancy). The area under the curve (AUC) quantified the overall diagnostic accuracy of the tests.

Results

The study demonstrated that IMA concentration was higher in both pleural fluid and serum of CHF patients compared with non-cardiac patients. PF and serum IMA demonstrated AUCs of 0.927 (95% CI: 0.844–1.00, P < 0.001), and 0.792 (95% CI: 0.653–0.930, P = 0.006), respectively, for diagnosing effusions due to CHF. The sensitivity and specificity of PF-IMA for CHF at the cut-off concentration of ≥1.0 absorbance units was 90% and 80%, respectively. Its negative predictive value (NPV) was quite high (96%). Positive correlation was found between PF-IMA concentrations and serum-IMA ( r = 0.540, P < 0.001).

Conclusions

Measuring IMA concentrations in serum and pleural fluid may be helpful in distinguishing pleural effusion due to a cardiac or non-cardiac aetiology.

Diagnostic accuracy of pleural fluid NT-pro-BNP for pleural effusions of cardiac origin: a systematic review and meta-analysis

Background

Several studies have been published in the literature on the diagnostic accuracy of NT-pro-BNP for pleural effusions from heart failure in the last decade. The purpose of our study was to perform a systematic review and meta-analysis on the diagnostic accuracy of pleural fluid NT-pro-BNP for pleural effusions of cardiac origin.

Methods

MEDLINE, EMBASE, PapersFirst, and the Cochrane collaboration and the Cochrane Register of controlled trials were searched. All searches were inclusive as of March 2010. Studies were only included if the absolute number of true-positive, false-negative, true-negative, and false-positive observations were available, and the "reference standards" were described clearly. Two investigators independently reviewed articles and extracted data. Quality was assessed with the Quality Assessment for Diagnostic Accuracy Studies (QUADAS). The bivariate model for diagnostic meta-analysis was used to obtain a pooled sensitivity and a pooled specificity.

Results

Ten studies (total number of patients 1120) were included in the meta-analysis. The average pleural fluid NT-pro-BNP level in effusions of cardiac origin was 6140 pg/mL. The pooled sensitivity and specificity of all studies combined was 94% (95% CI: 90-97) and 94% (95% CI: 89-97) respectively. The pooled positive likelihood ratio was 15.2 (95% CI: 8.1-28.7) and the pooled negative likelihood ratio was 0.06 (95% CI: 0.03-0.11). The area under the ROC curve was 0.98 (95% CI: 0.96-0.99) and the diagnostic odds ratio was 246 (95% CI: 81-745).

Conclusions

Pleural fluid NT-pro-BNP is a very useful biomarker with high diagnostic accuracy for distinguishing pleural effusions of cardiac origin.

Advances in the investigation and treatment of pleural effusions

Pleural effusions present a challenge for both diagnosis and treatment. They are a commonly presenting problem of a wide range of local and systemic potentially life threatening diseases and cause significant breathlessness. Significant advances have been made in the last 5 years in the diagnostic pathway and management options. This article reviews recent developments in the investigation of pleural effusions, particularly in pleural fluid analysis, biomarkers, imaging and pleural biopsy, and in the treatment of pleural infection and both malignant and benign effusions, including the use of indwelling pleural catheters. Although significant recent advances have been made in the management of pleural effusions, there the need still remains for further research if we are to reduce the morbidity and mortality caused by pleural effusions.

Comparison of pleural fluid N-terminal pro-brain natriuretic peptide and brain natriuretic-32 peptide levels

BACKGROUND

Current evidence indicates that measurement of pleural fluid N-terminal pro-brain natriuretic peptide (NT-proBNP) levels can aid in distinguishing pleural effusions of cardiac origin from those of noncardiac origin. To date, only one study, to our knowledge, has described simultaneous measurement of pleural fluid brain natriuretic-32 peptide (BNP) and NT-proBNP. The purpose of the present study was to determine pleural fluid BNP and NT-proBNP levels and analyze the relationship between these two measurements. We hypothesized that there would be a positive correlation between pleural fluid NT-proBNP and BNP, whereas NT-proBNP levels would be higher than BNP levels.

METHODS

Levels of pleural fluid NT-proBNP and BNP were measured by enzyme immunoassay in a total of 80 patients: 20 with congestive heart failure, 20 status post-coronary artery bypass graft, 20 with carcinoma, and 20 with pneumonia.

RESULTS

Comparison of NT-proBNP and BNP concentrations using the Spearman method of statistical analysis revealed a correlation coefficient of 0.572, P < .001. Evaluation of the diagnostic accuracy of BNP and NT-proBNP in patients with pleural effusions of cardiac origin demonstrated an area under the receiver operating characteristic curve of 0.700 (95% CI, 0.569-0.831) and 0.835 (95% CI, 0.721-0.949), respectively.

CONCLUSIONS

Although levels of pleural fluid BNP have a statistically significant correlation with those of NT-proBNP, this relationship only explains 32% of the variance in NT-proBNP levels. Furthermore, when compared with BNP, NT-proBNP is a more accurate diagnostic aid in the evaluation of pleural effusions of cardiac origin.

The importance of pleural fluid and serum NT-proBNP levels in differentiating pleural effusion due to heart failure from other causes of effusion

BACKGROUND AND OBJECTIVE

Pleural effusion due to congestive heart failure (CHF) typically are transudates. Light's criteria may be insufficient in determining if the pleural effusion is transudative or exudative in patients with CHF. The aim of our study was to assess the diagnostic performance of the amino-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) in pleural fluid and serum for the identification of pleural effusion owing to heart failure.

METHODS

The study prospectively evaluated NT-proBNP in serum and pleural fluid from patients with effusion owing to heart failure (n=51) and other causes (n=64). Measurements were made of levels of NT-proBNP by an electrochemiluminiscence immunoassay. The discriminative properties of NT-proBNP levels in identifying pleural effusion due to heart failure were determined by receiver operating characteristic curve (ROC) analysis and compared to the diagnostic value of finding a transudate by Light's criteria and serum-pleural fluid albumin gradients.

RESULTS

Serum and pleural fluid NT-proBNP levels were significantly elevated in patients with pleural effusion owing to heart failure. The area under ROC for the diagnosis of pleural effusion from heart failure was similar for pleural fluid (0.973, 95% CI: 0.914-0.995) and serum (0.968, 95% CI: 0.890-0.989) NT-proBNP.

CONCLUSION

NT-proBNP levels in either pleural fluid or serum have high diagnostic values and they are easily useable parameters in the diagnosis of heart failure-related pleural effusion.