Pleural fluid analysis: standstill or a work in progress?

Laboratory testing of extravascular body fluids: National recommendations on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine. Part I - Serous fluids

Extravascular body fluids (EBF) analysis can provide useful information in the differential diagnosis of conditions that caused their accumulation. Their unique nature and particular requirements accompanying EBF analysis need to be recognized in order to minimize possible negative implications on patient safety. This recommendation was prepared by the members of the Working group for extravascular body fluid samples (WG EBFS). It is designed to address the total testing process and clinical significance of tests used in EBF analysis. The recommendation begins with a chapter addressing validation of methods used in EBF analysis, and continues with specific recommendations for serous fluids analysis. It is organized in sections referring to the preanalytical, analytical and postanalytical phase with specific recommendations presented in boxes. Its main goal is to assist in the attainment of national harmonization of serous fluid analysis and ultimately improve patient safety and healthcare outcomes. This recommendation is intended to all laboratory professionals performing EBF analysis and healthcare professionals involved in EBF collection and processing. Cytological and microbiological evaluations of EBF are beyond the scope of this document.

Diagnostic Value of Vascular Endothelial Growth Factor, Transforming Growth Factor-β, Interleukin-8, and the Ratio of Lactate Dehydrogenase to Adenosine Deaminase in Pleural Effusion

PURPOSE

We studied the diagnostic value of cytokines, including vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β), and interleukin-8 (IL-8), and the ratio of lactate dehydrogenase (LDH) to adenosine deaminase (ADA) in pleural fluid.

METHODS

Prospective analysis of 44 inpatients or outpatients with pleural fluid, from December 2016 to March 2017 was conducted.

RESULTS

We enrolled patients with malignant pleural effusion (MPE, N = 15), empyema (N = 11), parapneumonic effusion (PPE, N = 7), chronic renal failure (CRF)/chronic heart failure (CHF) (N = 7), and tuberculous pleural effusion (TBPE, N = 4). The pleural fluid values of IL-8 and VEGF were significantly higher in empyema patients than in CRF/CHF or PPE patients. In all patients, the pleural fluid VEGF and IL-8 values were significantly positively correlated (r = 0.405, p = 0.006; r = 0.474, p = 0.047, respectively). TGF-β was elevated in patients with empyema, PPE, TBPE, and MPE. The pleural LDH-to-ADA ratio in patients with MPE or empyema/PPE was significantly higher than in patients with CRF/CHF or TBPE. LDH and ADA levels correlated significantly only in patients with MPE (r = 0.648, p = 0.009) and empyema/PPE (r = 0.978, p < 0.001).

CONCLUSIONS

VEGF and IL-8 production in the pleural cavity appear to accelerate the progression of PPE to empyema, by enhancing vascular permeability associated with inflammation. Sequential sampling would be needed to confirm this. The pleural LDH/ADA ratio may be a useful diagnostic tool for discriminating between various pleural effusion etiologies.

Systematic review and meta-analysis of vascular endothelial growth factor as a biomarker for malignant pleural effusions

Conventional methods may fail to identify the cause of pleural effusion (PE), thus establishing reliable biomarkers is deemed necessary. This study aimed at examining the role of vascular endothelial growth factor (VEGF) as a biomarker in the differentiation between malignant and benign PEs in adults. A comprehensive literature search in PubMed (Medline), Scopus (ELSEVIER), and Cochrane Central Register of Controlled Trials (CENTRAL) databases was conducted using keywords. We included studies that evaluated pleural and/or serum levels of VEGF among patients presenting with undiagnosed PE and the association between these levels and the final diagnosis. We performed a meta‐analysis to calculate the summary effect using the random effects model. Statistical analysis was performed with the statistical package for meta‐analysis Comprehensive Meta‐Analysis. Twenty studies were included in the systematic review, while 11 of them in the meta‐analysis. Pleural fluid VEGF levels among patients with malignant PE were increased by 1.93 ng/mL as compared to patients with benign PE (95% CI: 1.32–2.54, Q = 173, df (Q): 10, I² = 94.2%, P < 0.05). Serum VEGF levels among patients with malignant PE were increased respectively by 1.90 ng/mL (95% CI: 0.93–2.88, Q = 182, df (Q): 6, I² = 96.7%, P < 0.05). This study showed that malignant PEs were associated with higher levels of both pleural fluid and serum VEGF. VEGF appears to represent a promising biomarker for the differential diagnosis between benign and malignant PEs.

The impact of between analytical platform variability on the classification of pleural effusions into exudate or transudate using Light's criteria

BACKGROUND

Light's criteria are ratios of pleural fluid to serum total protein (TP), pleural fluid to serum lactate dehydrogenase (LDH) and pleural fluid LDH to the upper reference limit for serum LDH. They are used to classify pleural effusions into an exudate or transudate when pleural fluid protein is 25-35 g/L. We evaluated the impact of between analytical platforms on the classification of pleural effusions using Light's criteria.

METHODS

Light's criteria were used to classify pleural effusions with fluid TP between 25 and 35 g/L into exudate and transudate. LDH and TP were analysed using an Abbott ARCHITECT c16000 analyser using a lactate to pyruvate method for LDH and two Roche Cobas 800 c702 analysers, one using a lactate to pyruvate method (laboratory B) and one a lactate to pyruvate method (laboratory C).

RESULTS

Eighty-three paired serum and pleural fluid samples were analysed. Of these, 44 samples had a pleural fluid TP between 25 and 35 g/L and were classified according to Light's criteria. Classification of pleural fluid into transudate or exudate using different analytical platforms was 82% concordant. The LDH ratio and TP ratio were similar in laboratory B and laboratory C, but these were respectively lower (p<0.001) and higher (p<0.001) than those at laboratory A.

CONCLUSIONS

Although Light's criteria are ratios, which should minimise interassay variability, we report 18% discordance between different analytical platforms. The discordance was largely due to the performance of LDH and to a lesser extent protein assays in pleural fluid. Laboratories should be aware that assays may perform differently in serum and pleural fluid.

Reactive oxygen species measure for rapid detection of infection in fluids

BACKGROUND

Early detection of infection is critical to rapidly starting effective treatment. Diagnosis can be difficult, particularly in the intensive care unit (ICU) population. Because the presence of polymorphonuclear neutrophils in tissues is the hallmark of inflammatory processes, the objective of this proof of concept study was to determine whether the measurement of reactive oxygen species (ROS) could be an efficient diagnostic tool to rapidly diagnose infections in peritoneal, pleural and bronchoalveolar lavage (BAL) fluids in ICU patients.

METHODS

We prospectively included all patients hospitalized in the 21-bed surgical ICU of a teaching hospital from June 2010 to February 2014 who presented with systemic inflammatory response syndrome with suspicion of a peritoneal or pleural fluid or pulmonary infection needing a BAL. Instantaneous basal ROS production was measured in fluids and after phorbol 12-myristate 13-acetate (PMA) stimulation. We compared patients with infected fluids to those with non-infected fluids.

RESULTS

The overall ICU mortality rate was 34 %. A majority of patients were sampled following a delay of 5 days (2-12) after ICU admission, with most receiving antibiotics at the time of fluid sampling (71 %). Fluids were infected in 21/65 samples: 6/17 peritoneal fluids, 8/28 pleural fluids and 7/20 BALs. ROS production was significantly higher in the infected than in the non-infected group at baseline and after PMA stimulation in the peritoneal and pleural fluids but not in BAL.

CONCLUSION

Assessing instantaneous ROS production appears as a fast and reliable diagnostic method for detecting peritoneal and pleural fluid infection.

Hepatic hydrothorax: clinical features, management, and outcomes in 77 patients and review of the literature

Hepatic hydrothorax is an important and difficult-to-manage complication of cirrhosis and portal hypertension. Here, we aimed to study its clinical features and natural history. Complete clinical data, including outcomes, were abstracted from hospital records of patients with cirrhosis and ascites admitted to University of Texas Southwestern University teaching hospitals from January 2001 to July 2012. Hepatic hydrothorax was diagnosed based on currently accepted clinical characteristics of the disease, including a known diagnosis of cirrhosis, the presence of portal hypertension, pleural fluid analysis, and the absence of primary cardiopulmonary disease.Seventy-seven of 495 (16%) hospitalized cirrhotic patients with pleural effusion (28 female; mean age, 52 yr) met the criteria for diagnosis of hepatic hydrothorax. Resting dyspnea and cough were the most prominent presenting symptoms, occurring in 34% and 22% of patients, respectively. Pleural effusions were most often right-sided (56/77; 73%), followed by left-sided only (13/77; 17%) and bilateral effusions (8/77; 10%); 7 (9%) patients did not have detectable ascites. The mean Model for End-Stage Liver Disease (MELD) score at presentation was 16. The serum to pleural fluid albumin gradient (SPAG) was ≥1.1 in all 48 patients in whom it was measured. Most patients (64/77; 83%) were managed with diuretics and/or thoracentesis, while 8 (10%) underwent transjugular intrahepatic portosystemic shunt (TIPS) and 5 (7%) underwent liver transplant. A total of 44 of 77 (57%) patients died during a mean follow-up of 12 months. The average time from presentation to death for all patients was 368 days, while for those after TIPS it was 845 days. No deaths were reported in the liver transplant group. The data indicate that a substantial number of patients with hepatic hydrothorax had what may be considered atypical presentations, including left-sided only effusions, or pleural effusion without ascites. Here, we propose that the term "serum to pleural fluid albumin gradient (SPAG)" be used to describe the gradient between serum and pleural fluid albumin levels and suggest that not only is it consistent with the portal hypertensive pathophysiology of hepatic hydrothorax, but also it is a useful criterion for diagnosis of hepatic hydrothorax. Finally, the overall outcome of hepatic hydrothorax was extremely poor, except in those undergoing TIPS or liver transplantation.

Pleural, peritoneal and pericardial effusions - a biochemical approach

The pathological accumulation of serous fluids in the pleural, peritoneal and pericardial space occurs in a variety of conditions. Since patient management depends on right and timely diagnosis, biochemical analysis of extravascular body fluids is considered a valuable tool in the patient management process. The biochemical evaluation of serous fluids includes the determination of gross appearance, differentiation of transudative from exudative effusions and additional specific biochemical testing to assess the effusion etiology. This article summarized data from the most relevant literature concerning practice with special emphasis on usefulness of biochemical tests used for the investigation of pleural, peritoneal and pericardial effusions. Additionally, preanalytical issues concerning serous fluid analysis were addressed and recommendations concerning acceptable analytical practice in serous fluid analysis were presented.