Light's criteria revisited: consistency and comparison with new proposed alternative criteria for separating pleural transudates from exudates

New strategies to classify canine pleural effusions and the diagnostic value of acute phase proteins, amylase, and adenosine deaminase in pleural exudates

BACKGROUND

In dogs, simplified Light's criteria can discriminate transudates from exudates. Other tests used in human medicine are pleural effusion cholesterol (CHOLPE) and butyrylcholinesterase [BChEPE], the pleural effusion/serum ratio of these analytes (CHOLratio and BChEratio), and the serum albumin minus pleural effusion albumin gradient (SEAG).

OBJECTIVES

We aimed to assess the diagnostic accuracies of different biomarkers in dogs with pleural effusion in differentiating exudates from transudates. Secondarily, we evaluated the potential diagnostic utility of pleural effusion acute phase proteins, amylase, and adenosine deaminase in discriminating causes of exudative effusions.

METHODS

Cross-sectional study including 68 client-owned dogs with pleural effusion.

RESULTS

There were 48 exudates (10 septic, 16 neoplastic, 9 hemorrhagic, and 13 classified as other exudates) and 20 transudates. All the variables analyzed, except SEAG, were significantly different between exudates and transudates. Using the cut-off values adopted in human literature, accuracies for CHOLPE, CHOLratio, BChEPE, and BChEratio were between 82.35% and 85.29%; all values were significantly lower compared with the previously published simplified Light's criteria accuracy (i.e., 98%, p < .001 for all comparisons). We found the accuracy of the simplified Light's criteria to be similar to what has been previously reported (95.59%, p = .238). Paraoxonase-1 (PON-1PE) activity and the pleural effusion/serum paraoxonase-1 ratio (PON-1ratio) were significantly lower in exudative neoplastic effusions than in exudative hemorrhagic (p = .004 and p = .001) and septic (p = .004 and p < .001) effusions.

CONCLUSION

Simplified Light's criteria were the best method for discriminating transudates from exudates, and a low PON-1PE activity and PON-1ratio in exudative effusions may suggest an underlying neoplasia.

A retrospective analysis of transudative pleural effusion due to fibrosing mediastinitis

BACKGROUND

Pleural effusion caused by fibrosing mediastinitis is rarely reported. This study aimed to summarize the clinical manifestations, diagnosis and treatment of transudative pleural effusion due to fibrosing mediastinitis.

METHODS

Medical records and follow-up data of 7 patients with transudative pleural effusion due to fibrosing mediastinitis in Beijing Chaoyang Hospital between May 2014 and Feb 2018 were retrospectively analyzed.

RESULTS

These patients included 4 males and 3 females, with an average age of (64 ± 9) years. There were 3 left-sided effusions, 2 right-sided effusions and 2 bilateral effusions. Previous or latent tuberculosis was found in 6 patients. Pulmonary hypertension was indicated by echocardiography in all the 7 patients. Computed tomography pulmonary angiography (CTPA) of all the 7 cases showed increased soft tissue images visible in the mediastinum and bilateral hilus, different degrees of stenosis or occlusion in the pulmonary artery and pulmonary vein. In addition, 4 cases were found of right middle lobe atelectasis with a mediastinal window setting. There was interstitial pulmonary edema on the side of pleural effusion with a lung window setting. All the 7 patients were treated with intermittent drainage of pleural effusion combined with diuretic therapy. Five patients were treated with antituberculosis therapy. Up to now, two patients died of right heart failure and respiratory failure after 2 and 16 months respectively; The remaining 5 patients were still in follow up.

CONCLUSION

Fibrosing mediastinitis can lead to pulmonary vein stenosis or occlusion, and thus cause transudative pleural effusion, which can be detected by CTPA. Pulmonary hypertension, long time of cough, and a history of tuberculosis are common in these patients. The common therapy is intermittent drainage of pleural effusion combined with diuretic therapy.

Transudative Malignancy: Uncommon and Real

Light's criteria are the cornerstone to differentiate exudates from transudates. The traditional literature states that malignant pleural effusions are rarely transudative; therefore, cytology tends to be low yield and not a cost-effective decision. This case describes an 82-year-old female who developed a transudative pleural effusion despite having an underlying malignancy, highlighting the importance of integrating clinical judgment into pursuing thoracentesis with the cytological examination.

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.

Predictors of outcome of chest tube drainage of non-purulent exudative pleural effusions

Background

Although chest tube drainage is the primary management method for many pleural effusions, it has a failure rate of 9.4–48%. In this study, we examined the factors that predict the outcome of management of nonpurulent exudative effusions. The aim of this study was to determine the predictors of outcomes of chest tube drainage of pleural effusions.

Methodology

Consecutive patients who had a chest tube drainage of nonpurulent exudative pleural effusions were followed up in a prospective observational cohort study until extubation and discharge. Data on the management of the patients were recorded, analysed and compared between groups of patients with good and poor outcomes.

Results

Of the 52 patients studied, 38 had good outcomes, while 14 had poor outcomes. The mean±sd age was 39.7±15.9 years. Multivariate analysis demonstrated that empyema thoracis complicating drainage was an independent predictor of a poor outcome, while the duration of drainage ≤14 days and duration of illness before presentation <30 days were predictive of a good outcome.

Conclusion

Our results show that the development of empyema thoracis during drainage, a long duration of drainage and a prolonged period of illness before presentation are predictive of the outcome of chest tube drainage.

This study of predictors of outcome of chest drainage of nonpurulent pleural effusions found that the development of empyema, a prolonged duration of drainage and a prolonged duration of illness are predictive of a poor outcome of drainagehttps://bit.ly/3tpK39Y

Clinical characteristics and prognosis of serous body cavity effusions in patients with sepsis: a retrospective observational study

Background

Cavity effusion is common in patients with infectious diseases. However, the incidence rate and characteristics of serous cavity effusions (SCE) in septic patients are not clear to date. The objective of this study was to investigate the incidence and characteristics of SCE in septic patients and to explore the correlations between the bloody effusions and the illness severity/prognosis in septic patients.

Methods

From January 2010 to January 2015, a total of 214 patients with severe sepsis and septic shock were enrolled in this retrospective observational study. Thoracentesis or abdominal paracentesis was performed in 45 septic patients because of massive pleural effusions or ascites. The serum concentrations of VEGF, VEGFR, Ang, sICAM-1, sVCAM-1, E-selectin, Serpine1 and VE-cadherin in 45 septic patients underwent paracentesis were measured by enzyme-linked immunosorbent assay (ELISA).

Results

Of the 214 septic patients, 155 (72.4%) had SCE according to imaging or ultrasound manifestations. 45 subjects with SCE underwent therapeutic thoracentesis or abdominal paracentesis. Effusion laboratory analysis showed that exudates were predominant when compared with transudates (95.6% vs. 4.4%), and 16 (35.6%) patients suffered bloody effusions. Compared with patients with non-bloody effusions, those with bloody effusions showed higher critical illness scores (13 vs. 17 for APACHE II; 7 vs. 9 for SOFA), and higher mortality (6.9% vs. 62.5%). Moreover, patients with bloody effusions had delayed TT and APTT, increased D-dimer concentration, and higher serum levels of CRP and PCT (P < 0.05). In addition, the serum levels of Ang2, sVCAM-1 and E-selectin were significantly higher in patients with bloody effusions than in those with non-bloody effusions (P < 0.05). However, the serum level of VEGFR2 was lower in patients with bloody fluids (P = 0.025).

Conclusions

The incidence of serous cavity effusion is high in patients with sepsis. The septic patients with bloody effusions suffer a more inflammatory burden and a worse prognosis compared to septic patients with non-bloody effusions.

Improving the predictive accuracy of identifying exudative effusions

BACKGROUND

Application of Light's criteria results in misclassification of some transudative effusions as exudative, particularly because of congestive heart failure (CHF). We sought to determine if the serum to pleural fluid albumin (SF-A) and serum to pleural fluid protein (SF-P) gradients increased the predictive accuracy to correctly identify exudative effusions.

METHODS

We retrospectively analyzed 1,153 consecutive patients who underwent a diagnostic thoracentesis at the Medical University South Carolina. Univariable logistic regression analyses were used to determine the statistical significance of pleural fluid tests that correctly identified exudative effusions. Tests with significant diagnostic accuracy were combined in multivariable logistic regression models, with calculation of areas under the curve (AUCs) to determine their predictive accuracy. The predictive capability of the best model was compared with Light's criteria and other test combinations.

RESULTS

Pleural fluid lactate dehydrogenase (LDH), SF-A gradient, and SF-P gradient had a significant effect on the probability of identifying exudative pleural effusions. When combined together in a multivariable logistic regression, LDH (OR, 14.09 [95% CI, 2.25-85.50]), SF-A gradient (OR, 7.16 [95% CI, 1.24-41.43]), and SF-P gradient (OR, 6.83 [95% CI, 1.56-27.88]) had an AUC of 0.92 (95% CI, 0.85-0.98).

CONCLUSIONS

Application of Light's criteria, not uncommonly, misclassifies CHF transudative effusions as exudates. In cases where no cause for an exudative effusion can be identified or CHF is suspected, the sequential application of the fluid LDH, followed by the SF-P and then the SF-A gradients, may assist in reclassifying pleural effusions as transudates.

Can cholesterol be used to distinguish pleural exudates from transudates? evidence from a bivariate meta-analysis

Background

Many studies have investigated whether pleural cholesterol levels can aid in diagnosis of pleural exudates, and the results have varied considerably. To gain a more reliable answer to this question, we meta-analyzed the literature on using pleural cholesterol or the ratio of cholesterol in pleural fluid to cholesterol in serum (P/S cholesterol ratio) as diagnostic tests to help identify pleural exudates.

Methods

Literature databases were systematically searched for studies examining accuracy of pleural cholesterol or P/S cholesterol ratios for diagnosing pleural exudates. Data on sensitivity, specificity, positive/negative likelihood ratio (PLR/NLR), and diagnostic odds ratio (DOR) were pooled using bivariate-effects models. Summary receiver operating characteristic (SROC) curves and area under the curve (AUC) were used to summarize overall test performance.

Results

Our meta-analysis included up to 20 studies involving 3,496 subjects. Summary estimates for pleural cholesterol in the diagnosis of pleural exudates were as follows: sensitivity, 0.88 (95%CI 0.84 to 0.92); specificity, 0.96 (95% CI 0.92 to 0.98); PLR, 20.31 (95% CI 11.21 to 36.78); NLR, 0.12 (95% CI 0.09 to 0.17); DOR, 167.06 (95% CI 76.79 to 363.95); and AUC 0.97 (95% CI 0.95 to 0.98). The corresponding summary performance estimates for using the P/S cholesterol ratio were as follows: sensitivity, 0.94 (95% CI 0.92 to 0.96); specificity, 0.87 (95% CI 0.83 to 0.91); PLR 7.46 (95% CI, 5.47 to 10.19); NLR, 0.07 (95% CI 0.05 to 0.10); DOR, 107.74 (95% CI 60.91 to 190.60); and AUC 0.97 (95% CI 0.95 to 0.98).

Conclusions

Both pleural cholesterol level and the P/S cholesterol ratio are helpful for the diagnosis of pleural exudates. Nevertheless, the results of pleural cholesterol assays should be interpreted in parallel with the results of traditional tests and clinical information.

Video assisted rigid thoracoscopy in the diagnosis of unexplained exudative pleural effusion

INTRODUCTION

An undiagnosed exudative pleural effusion is often a difficult diagnostic dilemma that needs further histological study for a definitive etiological diagnosis. Video assisted rigid thoracoscopy is a minimally invasive procedure with a minor morbidity and mortality risk that could resolve this problem.

METHODS

Between January 2010 and December 2011, we performed thoracoscopy in 26 patients for diagnosis of undiagnosed exudative pleural effusion. Clinical and paraclinical data of patients were collected prospectively and analyzed.

RESULTS

Sole pleural effusion was the most common CT scan finding seen in 17 (65.4%) patients. Thoracoscopy was diagnostic in 24 patients (92.3%). The pathologic findings were carcinoma (46.2%), tuberculosis (30.8%) and chronic inflammation without a definitive microbiologic culture (15.4%). Surprisingly mean ADA level in the tuberculosis group was in normal range. No mortality or complication related to our operation was observed.

CONCLUSION

Video assisted thoracoscopy is a minimally invasive procedure with a high definitive diagnostic accuracy in the evaluation of tuberculosis and malignant pleural effusions. Pulmonologist should refer these patients sooner to decrease the waiting period of diagnosis and treatment of such conditions.

Solving the Light's criteria misclassification rate of cardiac and hepatic transudates

BACKGROUND AND OBJECTIVE

Pleural transudates are most commonly due to heart failure (HF) or hepatic hydrothorax (HH), but a number of these effusions are misclassified as exudates by standard (Light's) criteria. The aim of this study was to determine the prevalence of mislabelled transudates and to establish simple alternative parameters to correctly identify them.

METHODS

We retrospectively analysed the pleural fluid and serum protein, lactate dehydrogenase and albumin concentrations from 364 cardiac effusions and 102 HH. The serum-to-pleural fluid protein and albumin gradients (serum concentration minus pleural fluid concentration), as well as the pleural fluid-to-serum albumin ratio (pleural fluid concentration divided by the serum concentration) were calculated for the mislabelled transudates.

RESULTS

Light's criteria had misclassified more HF-associated effusions than HH (29% vs 18%, P = 0.002). A serum-to-pleural fluid protein gradient >3.1 g/dL correctly identified 55% and 61% of the HF and HH false exudates, respectively. The figures for an albumin gradient >1.2 g/dL were 83% and 62%. Finally, a pleural fluid-to-serum albumin ratio <0.6 had identical accuracy for labelling miscategorized cardiac and liver-related effusions (78% and 77%, respectively).

CONCLUSIONS

If the clinical picture is consistent with HF but the pleural fluid meets Light's exudative criteria, the measurement of the albumin rather than the protein gradient is recommended. In the context of cirrhosis, a potentially 'false' exudate is identified better by the pleural fluid-to-serum albumin ratio.

Biochemical constituents of peritoneal fluid in cows

Samples of peritoneal fluid and jugular venous blood were taken simultaneously from 95 clinically healthy Holstein-Friesian cows. The concentrations of total protein, albumin, glucose, cholesterol, fibrinogen, L-lactate and D-dimer, the activities of lactate dehydrogenase (LDH), alkaline phosphatase and creatine kinase, and the white blood cell count were determined in the samples. Light's criteria, the serum-ascites albumin gradient (SAAG) and the ratios of the concentration of each parameter in peritoneal fluid to its concentration in blood were calculated. The mean concentrations of total protein, albumin and D-dimer, the activity of LDH and the SAAG were different from the reference values for monogastric animals and human beings.

Classification tree analysis for the discrimination of pleural exudates and transudates

BACKGROUND

Classification and regression tree (CART) analysis is a non-parametric technique suitable for the generation of clinical decision rules. We have studied the performance of CART analysis in the separation of pleural exudates and transudates.

METHODS

Basic demographic, radiologic and laboratory data were retrospectively evaluated in 1257 pleural effusions (204 transudates and 1053 exudates, according to standard clinical criteria) and submitted for CART analysis. The model's discriminative ability was compared with that of Light's criteria, in both the original formulation and an abbreviated version, i.e., deleting the pleural fluid (PF)/serum lactate dehydrogenase (LDH) ratio from the triad.

RESULTS

A first CART model built starting from all available data identified PF/serum protein ratio and PF LDH ratios as the two best discriminatory parameters. This algorithm achieved a sensitivity of 96.8%, slightly lower than that of classical Light's criteria (98.5%) and comparable to that of the abbreviated Light's criteria (97.0%), and significantly better specificity (85.3%) compared to both classical (74.0%) and abbreviated (79.4%) Light's criteria. A second CART model developed after excluding serum measurements selected PF protein and PF LDH as the most discriminatory variables, and correctly classified 97.2% of exudates and 77.0% of transudates.

CONCLUSIONS

CART-based algorithms can efficiently discriminate between pleural exudates and transudates.

Prevalence and characteristics of pleural effusions in superior vena cava syndrome

OBJECTIVE AND BACKGROUND

The prevalence and characteristics of pleural effusions occurring in adults with the superior vena cava (SVC) syndrome are unknown. The purpose of the present study was to characterize these pleural effusions.

METHODS

Charts of patients diagnosed with SVC syndrome at a tertiary care referral centre were reviewed. Radiographs were evaluated for the presence and size of pleural effusions, presence and location of masses and mediastinal width. If a pleural effusion was present, the patient's chart and a pre-existing database on pleural effusions were searched to determine whether the effusion was sampled and the results of any laboratory investigations on the fluid.

RESULTS

The SVC syndrome occurred in 78 patients. Malignancy was the aetiology in 60% of the cases and bronchogenic carcinoma was the most common malignancy. An intravascular device was the aetiology in the majority of benign cases. Pleural effusion was found in 70% of patients with a malignant aetiology and 58% of those with a benign cause (P=0.345). The mean size of the effusions was larger in malignant cases (P=0.012). Of the 44 effusions 22 were sampled (17 in malignancy and five with benign processes); none was transudates, 20 (91%) were exudative (four of these were chylous) and the remaining two were reported as exudates but did not have pleural chemistries documented.

CONCLUSIONS

More than half of patients with SVC syndrome have pleural effusions, regardless of the aetiology. However, the effusions are larger when associated with malignancy. The majority of these effusions are exudative and occasionally chylous. None was transudates.

Apolipoproteína A1 y apolipoproteína B en los derrames pleurales

OBJECTIVE

To determine the levels of apolipoprotein A1 and apolipoprotein B in pleural effusions and analyze their possible diagnostic value.

PATIENTS AND METHODS

A total of 117 patients with pleural effusion (30 transudates and 87 exudates) were included. The apolipoproteins were measured by turbidimetry.

RESULTS

The apolipoprotein B values in serum were slightly lower in transudates than in exudates, and both apolipoproteins had lower values in patients with benign exudates than in malignant ones. The apolipoprotein levels in pleural fluid were lower in transudates than in exudates. The pleural/serum fluid ratios of both apolipoproteins were significantly lower in malignant effusions compared with benign exudates. No cutoff value was found that would make it possible to differentiate between transudates and exudates or between benign and malignant exudates with sensitivity or specificity levels that had clinical interest.

CONCLUSIONS

Apolipoprotein A1 and apolipoprotein B levels in pleural fluid are different in transudates and exudates, and the pleural/serum fluid ratios are also different between benign and malignant exudates. However, their measurement does not supply additional clinical information.

The separation of transudates and exudates with particular reference to the protein gradient

PURPOSE OF REVIEW

The separation of pleural transudates from exudates, as the first step in the study of pleural effusions of unknown cause, is generally accepted as a useful practice. However, the optimal way to do this remains moot.

RECENT FINDINGS

New and more sophisticated biochemical markers have been proposed together, with new approaches to the interpretation of the results. Nevertheless, new studies have consolidated the criteria of Light et al. as those with a better accuracy. Effective diuresis increases the concentration of most pleural biochemical parameters used to differentiate transudates from exudates and appears as the main cause of the failures of this dichotomic approach. Among the alternative criteria proposed for identifying transudates in the setting of diuresis, the total protein gradient between serum and pleural fluid seems to be the most cost effective.

SUMMARY

Together with clinical judgment, the use of biochemical criteria seems mandatory. The criteria of Light et al. remain those of election. In the setting of effective diuresis, the use of the protein gradient is recommended. Although new and more sophisticated markers have been tested, it seems that looking for the causes of misclassification, when applying the criteria that to date have shown better efficiency, deserves preferential investigation.

Pleural interleukin-1 beta in differentiating transudates and exudates: comparative analysis with other biochemical parameters

BACKGROUND

The differential diagnosis of pleural effusion is a frequent clinical problem. The possible role of pleural fluid cytokines in discriminating transudates from exudates has not been studied adequately.

OBJECTIVE

The aim of this study was to evaluate the serum and pleural fluid levels of interleukin-1 beta (IL-1 beta) and to compare it with common biochemical parameters such as cholesterol (CHOL), lactate dehydrogenase (LDH), total protein and albumin.

METHODS

One hundred and six consecutive patients with pleural effusion were studied. IL-1 beta was measured simultaneously in blood and pleural fluid using a radioimmunoassay. Standard laboratory methods were employed for biochemical parameters.

RESULTS

Using ROC analysis, a pleural IL-1 beta cutoff level 18.16 fmol/ml had a sensitivity of 76.8%, a specificity of 58.3% and a positive predictive value (PPV) 86.3% in the discrimination of transudates vs. all exudates. Serum IL-1 beta levels were higher in the nonmalignant group but without statistical difference compared with transudate patients. In addition, a significant difference was found between serum IL-1 beta in the malignant group in comparison with those of the transudate group (p < 0.01), also IL-1 beta levels were significantly increased in exudate effusion when compared with transudate (p < 0.001, p < 0.05, respectively). CHOL values of > or =65 mg/dl had 92.7% sensitivity, and 100% specificity and PPV for both.

CONCLUSIONS

The results of this study suggest that although IL-1 beta could be a marker with relatively good sensitivity and PPV for the differentiation of pleural effusion, the cost and time needed do not support its use as a routine laboratory test.

Is it meaningful to use biochemical parameters to discriminate between transudative and exudative pleural effusions?

OBJECTIVES

The usefulness of biochemical criteria to separate pleural transudates from exudates is controversial, and the limitations of Light's criteria in patients receiving diuretic therapy is of general concern. We evaluated the added value of biochemical criteria to clinical judgment for separating transudates from exudates.

SETTING

A community teaching hospital.

DESIGN

A prospective, observational study for the evaluation of diagnostic tests.

PATIENTS AND MEASUREMENTS

In 249 consecutive patients referred for diagnostic thoracentesis, two physicians classified the pleural effusion as transudate or exudate based on all available information just before performing the thoracentesis. The sensitivity, specificity, and accuracy of the clinical presumption were compared with those of Light's criteria, and serum-pleural fluid albumin and protein gradients. The combined accuracy of biochemical and clinical criteria was also assessed.

RESULTS

The accuracy of Light's criteria (93%) was significantly higher than that showed by the initial clinical presumption (84%; p < 0.01) and that of the alternative biochemical criteria: serum-pleural fluid albumin gradient (87%; p < 0.03) and serum-pleural fluid protein gradient (86%; p < 0.01). In patients receiving diuretic therapy, the accuracy of Light's criteria was 83% (60 of 72 cases), neither different to that of the albumin gradient (88%; 63 of 72 cases) nor to that of the protein gradient (86%; 62 of 72 cases). When these alternative biochemical criteria were applied exclusively to patients receiving diuretics who were thought to have a transudative effusion by clinical criteria, but having fluid identified as exudative by Light's criteria, the results did not improve significantly. Using a multiparametric model for the population receiving diuretics, the accuracy was greater (93%; 67 of 72 cases) than that of Light's criteria but without reaching statistical significance (p = 0.12).

CONCLUSIONS

Light's criteria are significantly superior to the clinical presumption to separate pleural transudates from exudates. In patients receiving diuretics, Light's criteria lose accuracy, which is similar to that showed by the use of alternative biochemical criteria alone or combined with clinical judgment.

Multilevel likelihood ratios for identifying exudative pleural effusions(*)

STUDY OBJECTIVES

To determine multilevel likelihood ratios for pleural fluid tests that are commonly used to discriminate between exudative and transudative pleural effusions.

DESIGN

Meta-analysis of patient-level data.

PATIENT DATA

Selected studies included patients with diagnoses of exudative or transudative pleural effusions who underwent thoracentesis and laboratory analysis of their pleural fluid.

MEASUREMENTS AND METHODS

Studies were identified by searching MEDLINE and related bibliographies. Data were obtained for 1,448 patients from seven primary investigators or extracted from dot plots in published reports. Likelihood ratios were calculated from extracted data stratified across ranges of test result values.

RESULTS

Sufficient data were available to calculate multilevel likelihood ratios for the elements of Light's criteria (pleural fluid lactate dehydrogenase [LDH], ratio of pleural fluid to serum LDH, and ratio of pleural fluid to serum protein), pleural fluid protein, ratio of pleural fluid to serum cholesterol, pleural fluid cholesterol, and gradient of pleural fluid to serum albumin. Each of these tests provided levels of likelihood ratios through the most clinically relevant range (0 to 10).

CONCLUSION

Multilevel likelihood ratios combined with a clinician's estimation of the pretest probability of an exudative effusion improve the diagnostic accuracy of discriminating between exudative and transudative pleural effusions. Likelihood ratios avoid the use of confusing terms, such as "pseudoexudates," that derive from the use of single cutoff points for pleural fluid tests.

Diagnostic value of interleukin-1alpha, interleukin-6, and tumor necrosis factor in pleural effusions

STUDY OBJECTIVES

Interleukin (IL)-1alpha, IL-6, and tumor necrosis factor (TNF)-alpha were measured in pleural fluid from 57 patients with pleural effusion in order to evaluate the diagnostic utility of these cytokines. We studied 20 patients with malignant pleural effusion, 11 patients with parapneumonic pleural effusion, 9 patients with tuberculous pleural effusion, and 17 patients with transudative pleural effusion. Cytokines were measured by radioimmunoassay.

SETTING

University tertiary hospital.

RESULTS

The mean values of the three cytokines measured in pleural fluid or in serum were significantly higher in patients with exudates than with transudates (p < 0.05). The ratio of IL-6 in pleural fluid to serum was significantly higher in exudates than in transudates (p < 0.05). The level of IL-6 in pleural fluid was significantly higher in tuberculous than malignant (p < 0.007) or parapneumonic pleural effusions (p < 0.04). No significant difference between the three types of exudates was found in pleural fluid levels of IL-1alpha or TNF-alpha.

CONCLUSIONS

Serum levels of IL-1alpha, TNF-alpha, and in particular IL-6 can distinguish exudates from transudates, while pleural fluid IL-6 levels could be useful as an additional marker in the differential diagnosis of tuberculous, malignant, and parapneumonic exudates. Finally, our results suggest that there is local cytokine production in exudative pleural effusions.

New criteria for the differentiation between transudates and exudates

AIMS

To investigate whether cholesterol and lactate dehydrogenase (LDH) measurements in fluids are more sensitive and specific markers for differentiating between exudates and transudates, as confirmed clinically, than the measurement of fluid total protein concentrations alone.

PATIENTS/METHODS

Serum, pleural fluid, and ascitic fluid from 61 unselected patients were analysed retrospectively for LDH, cholesterol, and total protein. Clinical classification of transudate or exudate was reached independently by reviewing clinical details and laboratory data.

RESULTS

Of 54 samples (40 pleural fluid and 14 ascitic fluid), 30 were classified clinically as exudates and 24 as transudates. Fluid LDH and fluid to serum protein ratio measurements were equally good at differentiating between exudates and transudates, with a sensitivity of 90%, a specificity of 79%, a positive predictive value (PPV) of 84%, and a negative predictive value (NPV) of 86%. A combination of these parameters improved sensitivity to 100% and NPV to 100%, but lowered the specificity to 71% and PPV to 81%. This combination achieved a higher efficiency than Light's criteria.

CONCLUSION

Routine measurement of fluid LDH values and the calculation of fluid to serum total protein ratios will aid in differentiating exudates from transudates.

[Prospective study of 1,000 consecutive patients with pleural effusion. Etiology of the effusion and characteristics of the patients]

OBJECTIVE

To describe the characteristics of patients with pleural effusion (PE) and the causes of PE in a prospective, consecutive series of patients.

SETTING

A tertiary care hospital associated with the Universidad Complutense de Madrid (Spain).

PATIENTS

One thousand consecutive patients with PE for whom clinical signs indicated the need for diagnostic thoracocentesis were studied prospectively in our service from December 1991 to July 2000.

RESULTS

The most common cause of PE was neoplasm (n = 364 patients). The most common place of origin of the tumor was the lung (n = 125), followed by the pleura (mesothelioma, n = 48). The most common histologic type was adenocarcinoma (n = 128). Tuberculosis was the second most common cause of PE (n = 155). PE was transudate in 118 patients, mainly secondary to heart failure. Among the 42 patients who were positive for human immunodeficiency virus (HIV), the most common cause of PE was tuberculosis. Tuberculosis was also the most likely cause of PE in patients under 40 years of age.

CONCLUSIONS

The most common causes of PE were neoplasm and tuberculosis. Tuberculosis was the most common cause in patients under 40 years of age and in those infected by HIV.

Cholesterol in the separation of transudates and exudates

The Light criteria represent the most acceptable method to separate transudates and exudates. However, approximately 10% of patients with transudates, especially those with congestive heart disease, are misdiagnosed with these criteria. To improve diagnostic accuracy, many biochemical markers have been proposed as alternatives to differentiate transudates and exudates. Cholesterol has raised particular interest because only pleural fluid is needed, which makes blood samples unnecessary and simplifies the procedure. In most clinical studies, cholesterol has been shown to be as sensitive as the Light criteria, although it is less specific. Other randomized studies are necessary to determine the real potential value of pleural-fluid cholesterol measurements. Studies of pleural-fluid cholesterol are aimed at better understanding the mechanisms by which cholesterol enters the pleural cavity and its role in diseases. The ideal cutoff point of cholesterol to differentiate transudates and exudates is still unknown. Recently, aspects of the cholesterol turnover in diseases have raised great interest. Cholesterol generated great interest after it was related to coronary artery diseases. The involvement of cholesterol in the atherosclerotic process is well known, although its importance in body cavities is still unclear.

Influence of diuretics on the concentration of proteins and other components of pleural transudates in patients with heart failure

PURPOSE

Diuretic therapy increases the total protein and lactate dehydrogenase concentrations in pleural fluid in patients with transudates due to heart failure, but the effect of diuresis on other substances in pleural fluid constituents is not known.

SUBJECTS AND METHODS

Twenty-one patients with transudative pleural effusions due to congestive heart failure were prospectively studied. Repeated diagnostic thoracentesis (mean +/- SD = 3 +/- 1; range, 2 to 6) was performed until the effusions were radiographically unapparent (5 +/- 2 days). Thirty-one patients with congestive heart failure who underwent only a single thoracentesis after diuretic therapy served as controls. We measured the concentrations of various components of pleural effusions in the serum and in the pleural fluid, and determined the serum-pleural fluid gradient (serum concentration minus pleural fluid concentration) and ratio (serum concentration divided by pleural fluid concentration).

RESULTS

The pleural concentrations of most components increased significantly (P <0.001) from the initial specimen to the final specimen: total protein, from 23 +/- 7 g/L to 33 +/- 9 g/L; albumin, from 13 +/- 4 g/L to 18 +/- 6 g/L; lactate dehydrogenase, from 177 +/- 62 U/L to 288 +/- 90 U/L; cholesterol, from 31 +/- 16 mg/dL to 52 +/- 22 mg/dL; and cholinesterase, from 1,304 +/- 616 U/L to 1,884 +/- 674 U/L. Expressed as percentage change, the increases in the serum-pleural fluid gradients for albumin (12% +/- 22%) and total protein (11% +/- 12%) were significantly less than the increases in their concentrations in pleural fluid (albumin, 47% +/- 49%; total protein, 48% +/- 40%) or in their pleural fluid/serum ratios (albumin, 27% +/- 29%; total protein, 38% +/- 34%).

CONCLUSIONS

The concentrations of the biochemical components commonly measured in pleural fluid increase progressively during diuretic therapy. Calculation of the serum-pleural fluid gradients for protein and albumin may be the most useful way to distinguish transudates from exudates in patients with congestive heart failure who have undergone diuresis.