Pleural SC5b-9: a test for identifying complicated parapneumonic effusions

Soluble Membrane Attack Complex: Biochemistry and Immunobiology

The soluble membrane attack complex (sMAC, a.k.a., sC5b-9 or TCC) is generated on activation of complement and contains the complement proteins C5b, C6, C7, C8, C9 together with the regulatory proteins clusterin and/or vitronectin. sMAC is a member of the MACPF/cholesterol-dependent-cytolysin superfamily of pore-forming molecules that insert into lipid bilayers and disrupt cellular integrity and function. sMAC is a unique complement activation macromolecule as it is comprised of several different subunits. To date no complement-mediated function has been identified for sMAC. sMAC is present in blood and other body fluids under homeostatic conditions and there is abundant evidence documenting changes in sMAC levels during infection, autoimmune disease and trauma. Despite decades of scientific interest in sMAC, the mechanisms regulating its formation in healthy individuals and its biological functions in both health and disease remain poorly understood. Here, we review the structural differences between sMAC and its membrane counterpart, MAC, and examine sMAC immunobiology with respect to its presence in body fluids in health and disease. Finally, we discuss the diagnostic potential of sMAC for diagnostic and prognostic applications and potential utility as a companion diagnostic.

Accuracy of complement activation product levels to detect infected pleural effusion in rats

BACKGROUND

Pleural empyema is a well-known complication of pneumonia. If treatment is delayed, empyema may increase morbidity and mortality in affected patients. Therefore, the identification of empyema biomarkers in parapneumonic pleural effusion is desirable. Previous research has suggested complement activation products as candidate empyema markers.

OBJECTIVE

To compare the levels of complement activation products C3a, C5a, and C5b9 in pleural effusion induced by Staphylococcus aureus (SA), Streptococcus pneumoniae (SP), or turpentine (control).

METHODS

Thirty-nine male Wistar rats (mean weight 414 g; 290-546 g) were allocated as follows: 17 animals in the SA group, 12 in the SP group, and 10 in the control group. Bacteria or turpentine were injected into the pleural space. After 12 hr, intrapleural fluid was collected using ultrasound-guided thoracentesis. Levels of complement activation products were determined using ELISA kits.

RESULTS

Two SA and one SP animals died before 12 hr. Mean levels were as follows: C3a: 1066.82 µg/ml (937.29-1196.35 µg/ml) in SA, 1188.28 µg/ml (1095.65-1280.92 µg/ml) in SP, and 679.13 µg/ml (601.29-756.98 µg/ml) in controls (P < 0.001); C5a: 55.727 ng/ml (41.22-70.23 ng/ml) in SA, 520.107 ng/ml (278.92-761.3 ng/ml) in SP, and 5.268 ng/ml (1.68-8.85 ng/ml) in controls (P < 0.001); C5b9: 15.02 ng/ml (13.1-16.94 ng/ml) in SA, 16.63 ng/ml (14.37-18.9 ng/ml) in SP, and 14.05 ng/ml (9.8-18.29 ng/ml) in controls (P = 0.692). ROC analysis revealed an area under the curve of 0.987 (95% CI: 0.953-1) for C3a; 1 (1-1) for C5a; and 0.757 for C5b9 (0.523-0.990).

CONCLUSIONS

In the present rat model, complement activation fragments C3a and C5a accurately detected infected pleural effusion. Pediatr Pulmonol. 2017;52:757-762. © 2017 Wiley Periodicals, Inc.

Distinguishing complicated from uncomplicated parapneumonic effusions

PURPOSE OF REVIEW

Treatment of parapneumonic effusions (PPEs) is challenged by the decision of whether or not to insert chest tubes. This review focuses on the factors that may aid in determining which patients require an immediate drainage of the pleural space, that is, have a complicated PPE.

RECENT FINDINGS

Clinical guidelines advocate the evaluation of radiological (large effusion or loculation), bacteriological (Gram-positive stain or culture), biochemical (pH < 7.20 or glucose <60 mg/dl), and macroscopic (pus) characteristics of the pleural fluid to assist in the identification of complicated PPEs. In the past few years, a number of new pleural fluid biomarkers have been tested for the same purpose, but with the exception of C-reactive protein (CRP), they should be considered investigative. A pleural fluid CRP higher than 100 mg/l or a serum CRP higher than 200 mg/l, when combined with pleural fluid pH or glucose, may greatly increase our capability to predict the need for instituting tube thoracostomy. Although some ultrasonographic and computed tomography features favor the diagnosis of pleural infection, their role in uncomplicated-complicated PPE discrimination has not been systematically evaluated.

SUMMARY

No pleural fluid tests, other than pH or glucose, have gained wide acceptance for the assessment of patients with PPE. However, if corroborated with further studies, the measurement of pleural fluid or serum CRP, in combination with the classical fluid parameters, may have the potential to be incorporated into medical decision making.

Management of Parapneumonic Pleural Effusion in Adults

Pleural infections have high morbidity and mortality, and their incidence in all age groups is growing worldwide. Not all infectious effusions are parapneumonic and, in such cases, the organisms found in the pleural space are not the same as those observed in lung parenchyma infections. The diagnostic difficulty lies in knowing whether an infectious effusion will evolve into a complicated effusion/empyema, as the diagnostic methods used for this purpose provide poor results. The mainstays of treatment are to establish an early diagnosis and to commence an antibiotic regimen and chest drain as soon as possible. This should preferably be carried out with fine tubes, due to certain morphological, bacteriological and biochemical characteristics of the pleural fluid. Fluid analysis, particularly pH, is the most reliable method for assessing evolution. In a subgroup of patients, fibrinolytics may help to improve recovery, and their combination with DNase has been found to obtain better results. If medical treatment fails and surgery is required, video-assisted thoracoscopic surgery (VATS) is, at least, comparable to decortication by thoracotomy, so should only undertaken if previous techniques have failed. Further clinical trials are needed to analyze factors that could affect the results obtained, in order to define new evidence-based diagnostic and therapeutic strategies that provide more effective, standardized management of this disease.

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.

Treatment of complicated pleural effusions in 2013

The incidence of pleural infection seems to be increasing worldwide. Despite continued advances in the management of this condition, morbidity and mortality have essentially remained static over the past decade. This article summarizes the current evidence and opinions on the epidemiology, etiology, and management of complicated pleural effusions caused by infection, including empyema. Although many parallels may be drawn between children and adults in such cases, most trials, guidelines, and series regard pediatric patient groups and those more than 18 years of age as separate entities. This review focuses mainly on the treatment of adult disease.

Diagnostic accuracy of biomarkers of oxidative stress in parapneumonic pleural effusions

BACKGROUND

The imbalance between oxidants and antioxidants is referred to as oxidative stress and has been associated with various respiratory disorders. The aim of this study was the assessment of 8-isoprostane (8-iso-PGF(2α)) and Cu/Zn superoxide dismutase (Cu/Zn SOD) in exudative pleural effusions in order to examine the diagnostic accuracy of these markers in the differentiation between complicated and uncomplicated parapneumonic effusions.

METHODS

The study included 214 consecutive patients with pleural effusions [68 parapneumonic (31 uncomplicated parapneumonic, 20 complicated parapneumonic, 17 empyemas), 24 tuberculous, 88 malignant and 34 transudates]. 8-Isoprostane and Cu/Zn SOD were determined by ELISA in pleural fluid and serum.

RESULTS

Parapneumonic effusions were characterized by higher pleural fluid 8-isoprostane levels compared to transudative, malignant and tuberculous effusions. Pleural fluid Cu/Zn SOD levels were lower in transudates, while serum levels were higher in transudative compared to all exudative pleural effusions. Both pleural fluid 8-isoprostane and Cu/Zn SOD were higher in complicated parapneumonic effusions and empyemas compared to uncomplicated parapneumonic effusions. Pleural fluid 8-isoprostane was the most accurate test to differentiate between complicated and uncomplicated parapneumonic pleural effusions with a sensitivity of 100% and a specificity of 58·1% at a cut-off point of 35·1 (AUC = 0·848).

CONCLUSIONS

Pleural fluid 8-isoprostane and Cu/Zn SOD may provide useful information for the differentiation between uncomplicated and complicated parapneumonic effusions and empyemas.

Proinflammatory cytokines, fibrinolytic system enzymes, and biochemical indices in children with infectious para-pneumonic effusions

BACKGROUND

In children, pleural empyema is a recognized complication of severe pneumonia and is characterized by loculated effusions with fibrin septations. The aim of this study was to evaluate the relationship between proinflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6], intrapleural fibrinolytic system enzymes [tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1)], and common biochemical indices during pleural infection.

METHODS

Children with pneumonia complicated by para-pneumonic effusions were enrolled into our study and underwent real-time chest sonography. The patients were divided into 3 groups by ultrasound using a recognized staging system of pleural effusions. Staging of progressive pleural infection was used to correlate with the characteristics of pleural effusions. The correlation of various pleural variables with the formation of complicated para-pneumonic effusions (CPE) was performed and pleural variables for predicting subsequent intervention procedures were also analyzed.

RESULTS

A total of 57 patients were enrolled in the present study. Univariate analysis revealed that the amounts of biochemical indices (pH, glucose, lactate dehydrogenase), proinflammatory cytokines (TNF-alpha, IL-1beta, IL-6), and fibrinolytic system enzymes (tPA, PAI-1) were significantly different with the progressive stages of para-pneumonic effusions (Ptrend < 0.05). For all proinflammatory cytokines, a positive correlation was found with lactate dehydrogenase and PAI-1, whereas a negative correlation was found with pH, glucose, and tPA. Moreover, these cytokines were also significantly correlated with PAI-1 in both non-CPE and CPE. The pleural fluid findings of IL-1beta (> or =50 pg/mL), PAI-1 (> or =1252 ng/mL), and pH (< or =7.30) were the most significant predictive factors for subsequent intervention procedures (P < 0.001).

CONCLUSIONS

The increased release of proinflammatory cytokines in pleural fluid caused by bacteria may result in an imbalance of the fibrinolytic system, which can subsequently lead to fibrin deposition and intervention procedures.

Role of pleural fluid C-reactive protein concentration in discriminating uncomplicated parapneumonic pleural effusions from complicated parapneumonic effusion and empyema

The aim of this study was to determine whether pleural fluid C-reactive protein (CRP) is useful in distinguishing complicated parapneumonic pleural effusion (CPPE) and empyema from uncomplicated parapneumonic pleural effusions (UPPE). A total of 69 consecutive patients with parapneumonic effusions were enrolled in the study: 29 with UPPE, 29 with CPPE, and 11 with empyema. Concentrations of standard biochemical parameters together with CRP in the pleural fluid were measured using an immunoturbidimetric assay. Pleural CRP was significantly higher in CPPE (11.6 mg/dl) and in empyema (12.2 mg/dl) than in UPPE (3.9 mg/dl). A cutoff value of 8.7 mg/dl for pleural CRP in the diagnosis of CPPE and empyema resulted in a sensitivity, specificity, and area under the receiver-operating characteristic curve (AUC) of 0.80, 0.97 and 0.94, respectively. Traditional lactic dehydrogenase (LDH) > or = 1000 U/L and glucose < or = 60 mg/dl can differentiate CPPE and empyema from UPPE, with the sensitivity, specificity, and AUC achieving 0.75/0.60.1.00/1.00,0.95/0.22, respectively. However, for the detection of CPPE and empyema, the combination of pleural fluid CRP > or = 8.7 mg/dl and LDH > or = 1000 U/L was valuable in achieving a sensitivity, specificity, and AUC of 0.97/1,00/0.95. This study suggests that measurement of pleural CRP can be useful in the workup of patients with a parapneumonic effusion in order to differentiate CPPE from UPPE.

Tumor Necrosis Factor-α in Pleural Fluid

STUDY OBJECTIVES

We sought to determine whether pleural fluid tumor necrosis factor (TNF)-alpha is a more accurate parameter to identify nonpurulent complicated parapneumonic effusion (CPPE) than the classical chemistries, namely pH, glucose, or lactate dehydrogenase (LDH).

METHODS

We studied 80 consecutive patients with parapneumonic effusions (35 with uncomplicated parapneumonic effusion [UPPE], 23 with nonpurulent CPPE, and 22 with empyema). Concentrations of standard biochemical parameters together with TNF-alpha were measured in pleural fluid, the latter by using an immunoenzymometric assay.

RESULTS

Pleural TNF-alpha was significantly higher in CPPE (133.0 pg/mL) and empyema (142.2 pg/mL) than in UPPE (39.1 pg/mL). A cut-off value of 80 pg/mL for pleural TNF-alpha resulted in a sensitivity, specificity, and area under receiver operating characteristic curve (AUC) of 78%, 89%, and 0.87, respectively, for the diagnosis of nonpurulent CPPE. A multivariate analysis selected both pleural TNF-alpha > or = 80 pg/mL and LDH > or = 1,000 U/L (sensitivity, 74%; AUC = 0.86), but excluded pleural glucose < or = 60 mg/dL (sensitivity, 39%; AUC = 0.82) and pH < or = 7.20 (sensitivity, 41%; AUC = 0.78), for identifying the need for drainage. The combined sensitivity of pleural fluid TNF-alpha and LDH was found to be 91%.

CONCLUSIONS

Pleural TNF-alpha may contribute to the identification of patients with nonpurulent CPPE with at least the same diagnostic accuracy, if not better, than the use of pH, glucose, or LDH.