Pleural LDH as a prognostic marker in adenocarcinoma lung with malignant pleural effusion

Enhanced diagnostic approaches for malignant pleural effusions: an extensive biochemical and statistical analysis

INTRODUCTION

Malignant pleural effusions are a common and debilitating complication of advanced malignancies, affecting approximately one million patients annually. This condition leads to significant morbidity and a decline in quality of life. Accurate diagnosis and effective management are critical yet challenging due to the overlap in biochemical markers between malignant and benign pleural effusions.

A novel bioassay reflecting response to immune checkpoint inhibitor therapy in non-small cell lung cancer with malignant pleural effusion

Background

Immune checkpoint inhibitor (ICI) therapy has prolonged the survival of a proportion of patients with advanced non-small cell lung cancer (NSCLC). Histological quantification of programmed cell death-ligand 1 (PD-L1) in tumors is a widely adopted marker for predicting the efficacy of ICI treatment. However, its use in patients with malignant pleural effusion (MPE) is occasionally challenging because of the difficulty of tissue sampling. The aim of this study was to identify new predictive factors for ICI treatment in patients with MPE.

Methods

A total of 22 patients with MPE were included. Initially, we surveyed several parameters of pleural effusion in relation to overall survival (OS). Next, we attempted to reflect the response to ICI treatment in vitro, a simple co-culture bioassay was designed, in which tumor cells and immune cells were co-cultured with nivolumab. Binding of nivolumab to T cells was confirmed by flow cytometry, and the released interferon-gamma (IFN-γ) was evaluated by enzyme-linked immunosorbent assay.

Results

The parameter analysis demonstrated that the levels of albumin and the percentage of lymphocyte were significantly correlated with OS in all patients. Vascular endothelial growth factor (VEGF) and high mobility group box 1 (HMGB1) were negatively correlated with OS in only driver gene mutation-positive patients. In vitro bioassay showed that nivolumab-binding T cells predominantly produced IFN-γ compared with control antibody. Of the 22 patients, 12 showed an increase in IFN-γ release after treatment with nivolumab. Despite the lack of significant correlations between IFN-γ levels and OS, the duration of ICI treatment tended to be longer in patients with IFN-γ release versus those without IFN-γ release.

Conclusions

This immune assay of IFN-γ release after treatment with nivolumab in vitro may identify responders prior to ICI treatment.

Development of a diagnostic algorithm to ascertain malignant pleural effusion utilizing clinical indicators and serum metal concentrations

Background

Malignant pleural effusion (MPE) is prevalent among cancer patients, indicating pleural metastasis and predicting poor prognosis. However, accurately identifying MPE in clinical settings is challenging. The aim of this study was to establish an innovative nomogram-derived model based on clinical indicators and serum metal ion levels to identify MPE.

Methods

From July 2020 to May 2022, 428 patients diagnosed with pleural effusion (PE) were consecutively recruited. Comprehensive demographic details, clinical symptoms, imaging data, pathological information, and laboratory results, including serum metal ion levels, were systematically collected. The nomogram was created by incorporating the most significant predictors identified through LASSO and multivariate logistic regression analysis. The predictors were assigned weighted points based on their respective regression coefficients, allowing for the calculation of a total score that corresponds to the probability of MPE. Internal validation using bootstrapping techniques assessed the nomogram's performance, including calibration, discrimination, and clinical applicability.

Results

Seven key variables were identified using LASSO regression and multiple regression analysis, including dyspnea, fever, X-ray/CT compatible with malignancy, pleural carcinoembryonic antigen(pCEA), serum neuron-specific enolase(sNSE), serum carcinoembryonic antigen(sCEA), and pleural lactate dehydrogenase(pLDH). Internal validation underscored the superior performance of our model (AUC=0.940). Decision curve analysis (DCA) analysis demonstrated substantial net benefit across a probability threshold range > 1%. Additionally, serum calcium and copper levels were significantly higher, while serum zinc levels were significantly lower in MPE patients compared to benign pleural effusion (BPE) patients.

Conclusion

This study effectively developed a user-friendly and reliable MPE identification model incorporating seven markers, aiding in the classification of PE subtypes in clinical settings. Furthermore, our study highlights the clinical value of serum metal ions in distinguishing malignant pleural effusion from BPE. This significant advancement provides essential tools for physicians to accurately diagnose and treat patients with MPE.

Development and validation of the CAIL prognostic score in non-small cell lung cancer patients with malignant pleural effusion

BACKGROUND

Patients with malignant pleural effusion (MPE) typically have poor prognoses, and predicting survival is challenging. The present study aimed to identify prognostic factors of overall survival (OS) in non-small cell lung cancer (NSCLC) patients with MPE in the time of immunotherapy and targeted therapy.

METHODS

Data of 344 consecutive NSCLC patients with MPE on clinical, radiological, and molecular characteristics and treatment options were collected. The risk factors in the training cohort were assessed using univariate and multivariate proportional hazards analyses. A clinical prognostic score was established and validated.

RESULTS

According to the results of the multivariable survival analysis, the Eastern Cooperative Oncology Group (ECOG) performance score (PS), antiangiogenic therapy, immunotherapy, and lactic dehydrogenase (LDH) in pleural fluid (CAIL) prognostic score was developed (n = 275) and subsequently validated (n = 69). Patients who underwent risk stratification into low-, moderate-, and high-risk groups had median OS of 46.1, 23.1, and 9.6 months, respectively (P < 0.0001). The area under the curve (AUC) analysis showed the CAIL score to be superior at predicting survival compared with the LENT score at 6 (0.84 vs. 0.77, P < 0.01), 12 (0.87 vs. 0.82, P < 0.01), and 36 months (0.80 vs. 0.77, P < 0.01).

CONCLUSIONS

For NSCLC patients with MPE, the validated CAIL prognostic score integrates clinical characteristics and therapeutic modalities to predict survival.

Risk factors for symptomatic malignant pleural effusion recurrence in patients with actionable mutations in advanced lung adenocarcinoma

Background

Malignant pleural effusion (MPE) comes generally with high mortality and poor prognosis. Recurrence of symptomatic MPE is always accompanied by poor survival quality. In lung adenocarcinoma, researchers speculate whether patients with actionable mutation or without are applicable to different management models for MPE. Under the background of the high mutation probability and the encouraging therapeutic response in Asians, researches on the risk factors of MPE are in need.

Methods

This retrospective review included 343 metastatic lung adenocarcinoma patients with MPE. Recurrence was defined as recurrent symptomatic MPE requiring the second thoracentesis to relieve symptoms within 300 days after the first thoracentesis. Univariable and multivariable Cox regression analysis were utilized to investigate independent risk factors for MPE recurrence.

Results

Of the 343 patients involved, 139 experienced MPE recurrence within 300 days; 34.3% in 201 patients with actionable mutations and 51.2% in 129 patients without actionable mutations are in the recurrence. The median recurrence-free survival (RFS) of the group without mutations was 161 days. The median RFS of the other group with mutations was 300 days. Patients with actionable mutations showed a significantly lower hazard of MPE recurrence on univariate analysis. The multivariate analysis indicated that receiving targeted therapy after the first thoracentesis within 30 days, lower neutrophil-to-lymphocyte ratio (NLR) level, lower serum lactate dehydrogenase (s-LDH) level, and lower serum carcinoembryonic antigen (s-CEA) level were independent protective factors. In subgroup analysis, risk factors differed. Receiving targeted therapy after the first thoracentesis within 30 days remained an independent factor in the mutated patients.

Conclusions

The findings herein indicated the characteristics of specific patients at high risk for MPE recurrence in lung adenocarcinoma. Patients with actionable mutations benefit more in MPE recurrence and could benefit from targeted therapy and active intrapleural management.

Pleural Fluid Resolution Is Associated with Improved Survival in Patients with Malignant Pleural Effusion

Malignant pleural effusion is associated with a poor prognosis and, while risk stratification models exist, prior studies have not evaluated pleural fluid resolution and its association with survival. We performed a retrospective review of patients diagnosed with malignant pleural effusion between 2013 and 2017, evaluating patient demographics, pleural fluid and serum composition, and procedural and treatment data using Cox regression analysis to evaluate associations with survival. In total, 123 patients were included in the study, with median survival from diagnosis being 4.8 months. Resolution of malignant pleural fluid was associated with a significant survival benefit, even when accounting for factors such as placement of an indwelling pleural catheter, anti-cancer therapy, pleural fluid cytology, cancer pheno/genotypes, and pleural fluid characteristics. Elevated fluid protein, placement of an indwelling pleural catheter, and treatment with targeted or hormone therapies were associated with pleural fluid resolution. We conclude that the resolution of pleural fluid accumulation in patients with malignant pleural effusion is associated with a survival benefit possibility representing a surrogate marker for treatment of the underlying metastatic cancer. These findings support the need to better understand the mechanism of fluid resolution in patients with malignant pleural effusion as well as the tumor-immune interplay occurring with the malignant pleural space.

Echographic septation: A potentially useful indicator discriminating tuberculous from malignant pleural effusion

BACKGROUND

Tuberculous (TBE) and malignant (MPE) pleural effusions present with similar lymphocytic exudates. As TBE is an inflammatory and hypersensitivity process, we hypothesized that echographic septation may be more prevalent in TBE than in MPE, potentially serving as a good clinical predictor for TBE.

METHODS

A total of 183 TBE and 266 MPE patients were recruited retrospectively. Multivariate logistic regression was performed to determine significant predictors for TBE.

RESULTS

TBE diagnosis was confirmed histologically (caseating granuloma) in 84.7% of the cases, while MPE was biopsy-proven in 63.9% of the cases. Echographic septation was more evident in TBE than in MPE (46.5% vs. 8.2%, p < 0.001). Multivariate logistic regression analysis showed that male sex, serum leucocyte count ≤9 × 10⁹/L or pleural fluid protein ≥50 g/L, and echographic septation (aOR: 9.28, p < 0.001) were independent predictors for TBE. These parameters collectively provided a diagnostic accuracy of 79.61% (95% CI 74.13-84.38).

CONCLUSIONS

Echographic septation may potentially facilitate discrimination between TBE and MPE as part of a clinical prediction model. Prospective validation of this prediction model in an external cohort is anticipated.

Total Protein-Chloride Ratio in Pleural Fluid Independently Predicts Overall Survival in Malignant Pleural Effusion at the First Diagnosis

Objective

Pre-treatment biomarkers to estimate overall survival (OS) for malignant pleural effusion (MPE) are unidentified, especially those in pleural fluid. We evaluated the relationship between OS and total protein–chloride ratio in malignant pleural effusion (PE TPClR).

Materials and Methods

A retrospective study was undertaken to identify patients from 2006 to 2018 who had pathologically or cytologically confirmed MPE and received no tumor-targeted therapy. We recorded the pre-treatment clinicopathologic characteristics and follow-up status. OS was estimated by the Kaplan–Meier method, and the association between variables and OS was evaluated by Cox proportional hazards models.

Results

We screened 214 patients who met the eligibility criteria. The optimal cutoff value for the PE TPClR was set at 0.53. The univariate analysis showed that there was a significant correlation between PE TPClR and OS (P < 0.001). The multivariate analysis between OS and the variables selected from the univariate analysis showed that the levels of neutrophil, alkaline phosphatase, neuron-specific enolase, platelets, albumin in peripheral blood, and white blood cells in pleural effusion were also independent predictors of OS.

Conclusion

In patients with MPE, pre-treatment PE TPClR independently predicts OS. Although further research is necessary to generalize our results, this information will help clinicians and patients to determine the most appropriate treatment for MPE patients.

Serum lactate dehydrogenase activities as systems biomarkers for 48 types of human diseases

Most human diseases are systems diseases, and systems biomarkers are better fitted for diagnostic, prognostic, and treatment monitoring purposes. To search for systems biomarker candidates, lactate dehydrogenase (LDH), a housekeeping protein expressed in all living cells, was investigated. To this end, we analyzed the serum LDH activities from 172,933 patients with 48 clinically defined diseases and 9528 healthy individuals. Based on the median values, we found that 46 out of 48 diseases, leading by acute myocardial infarction, had significantly increased (p < 0.001), whereas gout and cerebral ischemia had significantly decreased (p < 0.001) serum LDH activities compared to the healthy control. Remarkably, hepatic encephalopathy and lung fibrosis had the highest AUCs (0.89, 0.80), sensitivities (0.73, 0.56), and specificities (0.90, 0.91) among 48 human diseases. Statistical analysis revealed that over-downregulation of serum LDH activities was associated with blood-related cancers and diseases. LDH activities were potential systems biomarker candidates (AUCs > 0.8) for hepatic encephalopathy and lung fibrosis.

A retrospective study on the combined biomarkers and ratios in serum and pleural fluid to distinguish the multiple types of pleural effusion

Purpose

Pleural effusion (PE) is a common clinical manifestation, and millions of people suffer from pleural disease. Herein, this retrospective study was performed to evaluate the biomarkers and ratios in serum and pleural fluid (PF) for the differential diagnosis of the multiple types of PE and search for a new diagnostic strategy for PE.

Methods

In-patients, who developed tuberculous PE (TPE), malignant PE (MPE), complicated parapneumonic effusion (CPPE), uncomplicated PPE (UPPE), or PE caused by connective tissue diseases (CTDs) and underwent thoracentesis at Peking University People’s Hospital from November 2016 to April 2019, were included in this study. Eleven biomarkers and their ratios in serum and PF were investigated and compared between pairs of the different PE groups, and a decision-tree was developed.

Results

Totally 112 PE cases, including 25 MPE, 33 TPE, 19 CPPE, 27 UPPE, and 8 PE caused by CTDs, were reviewed. Biomarkers and ratios showed good diagnostic performance with high area under the curve values, sensitivities, and specificities for the differential diagnosis of the multiple types of PE. According to the decision-tree analysis, the combination of adenosine deaminase (ADA), serum albumin, serum lactate dehydrogenase, total protein, PF-LDH/ADA, and PF-LDH/TP provided the best predictive capacity with an overall accuracy of 84.8%; the sensitivity and specificity for TPE diagnosis were 100% and 98.7%, respectively.

Conclusion

The biomarkers and ratios showed good diagnostic performance, and a decision-tree with an overall accuracy of 84.8% was developed to differentiate the five types of PE in clinical settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01459-w.

Breathlessness Predicts Survival in Patients With Malignant Pleural Effusions: Meta-analysis of Individual Patient Data From Five Randomized Controlled Trials

BACKGROUND

Patients with malignant pleural effusions (MPEs) experience breathlessness and poor survival. Breathlessness is associated with poor survival in other conditions.

RESEARCH QUESTION

Is breathlessness, measured using a visual analog scale for dyspnea (VASD), associated with survival in patients with MPE?

STUDY DESIGN AND METHODS

Individual patient data from five randomized controlled trials of 553 patients undergoing interventions for MPE were analyzed. VASD was recorded at baseline and daily after intervention. Patients were followed up until death or end of trial. Univariate and multivariable Cox regression were used to identify factors associated with survival.

RESULTS

Baseline VASD was significantly associated with worse survival, with a hazard ratio of 1.10 (95% CI, 1.06-1.15) for a 10-mm increase in VASD. On multivariable regression, it remained a significant predictor of survival. Mean 7-day VASD and mean total VASD were also predictors of survival (mean 7-day VASD: hazard ratio [HR], 1.26 [95% CI, 1.19-1.34]; total VASD: HR, 1.25 [95% CI, 1.15-1.37]). Other predictors of survival were serum C-reactive protein level and tumor type. Previous treatment with chemotherapy, performance status, pleural fluid lactate dehydrogenase, serum albumin, hemoglobin, serum neutrophil:lymphocyte ratio, and size of effusion were associated with survival on univariate but not multivariable analysis.

INTERPRETATION

Breathlessness, measured using VASD at baseline and postprocedure, is a predictor of survival in patients with MPE.

Development of RECLS score to predict survival in lung cancer patients with malignant pleural effusion

Background

Malignant pleural effusion (MPE) is usually caused by lung cancer, and the prognostic factors are poorly understood. We aimed to develop models to predict the survival of lung cancer patients and lung adenocarcinoma patients with MPE.

Methods

We enrolled lung cancer patients with MPE in Nanjing Jinling Hospital from January 2008 to June 2018 into our study. We selected risk factors using multivariable Cox proportional-hazards analysis in the development cohort. The risk models were created according to the risk ratio (RR) value. The participants were categorized into low-risk, moderate-risk, and high-risk groups according to the sum of every risk factor.

Results

A total of 367 lung cancer patients were included in the development cohort. The scoring systems RECLS (relapse or not, ECOG PS, CRP, pleural LDH, and TNM stage) and RECLSAM (relapse or not, ECOG PS, CRP, pleural LDH, TNM stage, albumin-globulin ratio, and activating gene mutation) were created for lung cancer patients with MPE and lung adenocarcinoma patients with MPE. The area under the curve (AUC) values for the RECLS model were 0.911, 0.845, and 0.754, respectively, at 1 month, 6 months, and 12 months.

Conclusions

This study developed prognostic models for lung cancer patients with MPE. The RECLS and RECLSAM scores are practical, clinically applicable models to help guide the selection of optimal treatment strategies.

Pleural effusion as an isolated finding in COVID-19 infection

Common radiological findings of COVID -19 infection include bilateral ground-glass opacities in lower lobes with a peripheral distribution. Pleural effusion is considered a rare manifestation of COVID -19 infection. We present a 52 years old patient with a three-week history of right-sided pleuritic chest pain, fever, and dyspnea. Laboratory investigations revealed high C-reactive protein and ferritin levels and a positive COVID-polymerase chain reaction (PCR) from a nasopharyngeal swab. Chest X-ray and Computed tomography (CT) identified a moderate right-sided pleural effusion, which was exudative with mixed cellularity and high Lactate dehydrogenase (LDH). Histopathology of thoracoscopic pleural biopsy didn't reveal granulomas, malignancy, or any microbiological growth. We postulate that having ruled out any other cause the effusion was likely related to the Covid-19 infection. Our case highlights that COVID-19 can present with isolated pleural effusions, therefore it should be kept as an etiology of effusions especially if other possible causes have been ruled out.

Prognostic value of a new score using serum alkaline phosphatase and pleural effusion lactate dehydrogenase for patients with malignant pleural effusion

BACKGROUND

The objective of our study was to analyze the prognostic value of the combination of serum ALP and pleural effusion LDH (AL score) for malignant pleural effusion (MPE) patients.

METHODS

This study includes retrospective, descriptive and observational research from 1 June 2006 to 1 December 2017, which aimed to identify prognostic factors related to MPE patients. We analyzed the association of various clinical features, routinely tested markers from peripheral blood and MPE at diagnosis and overall survival (OS). All MPE patients were assigned to three groups according to their AL score. The impact of the AL score and other prognostic factors were evaluated with multivariable regression.

RESULTS

According to their AL score, 193 patients were assigned to three groups with 25 in group 0 (sALP < 65 U/L and pLDH < 155 U/L), 121 in group 1 (sALP > 65 U/L or pLDH > 155 U/L) and 47 (sALP > 65 U/L and pLDH > 155 U/L) in group 2. For groups 0, 1 and 2, median survival times (MST) were 23, 15 and 7 months, respectively. Among the three groups, MST, serum albumin level, C reactive protein, erythrocyte sedimentation rate, the ratios of platelet-to-lymphocyte, neutrophil-to-lymphocyte showed significant differences. The counts of neutrophils, monocytes, platelets and AL score (0 vs. 1, P = 0.038, hazard ratio [HR]: 1.858, 95% confidence interval [CI]: [1.034, 3.339]; 0 vs. 2, P = 0.001, HR: 2.993, 95% CI: [1.556, 5.531]) were independent prognostic indicators for OS of MPE patients.

CONCLUSION

AL score is a promising indicator which can be used to predict the prognosis of MPE patients. It can assist physicians in the selection of patients for appropriate palliative treatment.

KEY POINTS

To our knowledge, this paper is the first study that combined two enzymes (sALP and pLDH) from serum and pleural effusion and studied the prognostic value for MPE patients. It has been proved to be a promising indicator to assist physicians select patients for appropriate palliative treatment.

Interpreting pleural fluid results

Interpreting pleural fluid results correctly requires an awareness of the possible aetiologies of a pleural effusion and an understanding of the reliability of the outcome of each investigation. All results must be interpreted within each different clinical context and knowledge of the pitfalls for each test is necessary when the diagnosis is unclear. This review aims to discuss the common aetiologies of a pleural effusion and some of the pitfalls in interpretation that can occur when the diagnosis is unclear.

Polyserositis: a diagnostic challenge

BACKGROUND

Polyserositis (PS) is the inflammation, with effusion, of different serous membranes. It has been associated with different aetiologies, but the aetiology of PS remains unknown in a high percentage of patients.

AIMS

The general objective of this retrospective study was to analyse the aetiology of PS cases seen at Son Llàtzer Hospital in an 11-year period. Other objectives were to determine the epidemiological, clinical and analytical characteristics of these patients.

METHODS

An observational, descriptive and retrospective study to analyse the aetiology of PS cases seen at Son Llàtzer Hospital. The inflammation of two or more serous membranes confirmed by an imaging test was required and at least one of the serous fluid should be an exudate.

RESULTS

A total of 92 patients was included in the study. The most common diagnosis was neoplasm (nearly one-third of cases) followed by infectious and autoimmune diseases. PS aetiology was unknown in more than one-third. Pleura and pericardium were the most common sites of serosal involvement (83%). Antinuclear antibodies' positivity in serum and increased levels of adenosine deaminase in pleural effusion were significantly associated with a final diagnosis of autoimmune disease. Increased pleural lactate dehydrogenase levels were significantly associated with a final diagnosis of neoplasm. In 9 of 14 patients with a previous cancer, PS represented a recurrence of their cancer. Cases of unknown aetiology presented most frequently as pleural and pericardial involvement, and the majority resolved. In very few patients, an infectious aetiology could be proven.

CONCLUSION

PS is a frequent clinical entity that is associated with different diseases and its diagnosis could be challenging, with a high rate of unknown aetiologies.

Prognostic Significance of Blood, Serum, and Ascites Parameters in Patients with Malignant Peritoneal Mesothelioma or Peritoneal Carcinomatosis

To determine effects of the biochemical and cytological properties of blood, serum, and ascites on survival of patients with malignant peritoneal effusion (MPeE), including malignant peritoneal mesothelioma (MPeM) and peritoneal carcinomatosis (PC), we conducted a retrospective study of patients with MPeE and healthy controls. Potential prognostic factors were identified as follows: age, sex, blood neutrophil-to-lymphocyte ratio (NLR), serum parameters, ascites parameters, serum-ascites albumin gradient, and the ascites-serum LDH ratio. Compared to those of the control group, serum albumin levels were significantly lower, and the NLR and serum LDH levels were significantly higher in the MPeE group. Overall survival (OS) was longer in patients with MPeM compared to that in patients with PC. Compared with patients in the MPeM, patients with PC had higher NLRs, ascites glucose levels, serum-ascites albumin gradients, and serum LDH levels. In contrast, their ascites albumin levels and ascites-serum LDH ratios were lower. Univariate analyses indicated that the NLR, serum LDH levels, ascites LDH levels, ascites coenocyte levels, and the ascites coenocyte-to-monocyte ratios affected the OS. Multivariate analyses identified only serum and ascites LDH levels as independent prognostic factors.

The pleural fluid lactate dehydrogenase/adenosine deaminase ratio differentiates between tuberculous and parapneumonic pleural effusions

Background

Although pleural fluid lactate dehydrogenase (LDH) and adenosine deaminase (ADA) levels are often used to distinguish between tuberculous pleural effusion (TPE) and parapneumonic pleural effusion (PPE), this can be challenging as the LDH level may vary from normal to severely increased in PPE and a significantly elevated ADA is frequently measured in both conditions. In this study, we evaluated use of the pleural fluid LDH/ADA ratio as a new parameter to discriminate TPE from PPE.

Methods

A retrospective study was conducted in patients with pathologically-confirmed TPE (n = 72) and PPE (n = 47) to compare pleural fluid LDH and ADA levels and LDH/ADA ratios between the 2 groups. A receiver operating characteristic (ROC) curve was constructed for identifying TPE.

Results

The median pleural fluid LDH and ADA levels and LDH/ADA ratios in the TPE and PPE groups were: 364.5 U/L vs 4037 U/L (P < .001), 33.5 U/L vs 43.3 U/L (P = .249), and 10.88 vs 66.91 (P < .0001), respectively. An area under the ROC curve of 0.9663 was obtained using the LDH/ADA ratio as the indicator for TPE identification, and the sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were, respectively, 93.62%, 93.06%, 13.48, and 0.068 at a cut-off level of 16.20.

Conclusions

The pleural fluid LDH/ADA ratio, which can be determined from routine biochemical analysis, is highly predictive of TPE at a cut-off level of 16.20. Measurement of this parameter may be helpful for clinicians in distinguishing between TPE and PPE.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0526-z) contains supplementary material, which is available to authorized users.