Validation of leukotriene B4 measurements in exhaled breath condensate

Non-volatile compounds in exhaled breath condensate: review of methodological aspects

In contrast to bronchial and nasal lavages, the analysis of exhaled breath condensate (EBC) is a promising, simple, non-invasive, repeatable, and diagnostic method for studying the composition of airway lining fluid with the potential to assess lung inflammation, exacerbations, and disease severity, and to monitor the effectiveness of treatment regimens. Recent investigations have revealed the potential applications of EBC analysis in systemic diseases. In this review, we highlight the analytical studies conducted on non-volatile compounds/biomarkers in EBC. In contrast to other related articles, this review is classified on the basis of analytical techniques and includes almost all the applied methods and their methodological limitations for quantification of non-volatile compounds in EBC samples, providing a guideline for further researches. The studies were identified by searching the SCOPUS database with the keywords "biomarkers," "non-volatile compounds," "determination method," and "EBC."

A novel monoclonal antibody suitable for the detection of leukotriene B4

Leukotriene B4 as an inflammatory mediator is an important biomarker for different respiratory diseases like asthma, chronic obstructive pulmonary disease or cystic lung fibrosis. Therefore the detection of LTB4 is helpful in the diagnosis of these pulmonary diseases. However, until now its determination in exhaled breath condensates suffers from problems of accuracy. Reasons for that could be improper sample collection and preparation methods of condensates and the lack of consistently assay specificity and reproducibility of the used immunoassay detection system. In this study we describe the development and the characterization of a specific monoclonal antibody (S27BC6) against LTB4, its use as molecular recognition element for the development of an enzyme-linked immunoassay to detect LTB4 and discuss possible future diagnostic applications.

Determination of urinary levels of leukotriene B(4) using ad highly specific and sensitive methodology based on automatic MEPS combined with UHPLC-PDA analysis

Leukotriene B4 (LTB4) is a potent mediator of inflammation and plays a key function in the pathophysiology of chronic asthma. Detectable urinary levels of LTB4, arises from the activation of leukotriene pathways. In this study an ultra-fast, selective and sensitive analytical method based on semi-automatic microextraction by packed sorbents (MEPS) technique, using a new digitally controlled syringe (eVol®) combined with ultra-high pressure liquid chromatography (UHPLC), is proposed for the measurement of urinary LTB4 (U-LTB4) levels in a group of asthmatic patients (APs) and healthy controls (CTRL). Important parameters affecting MEPS performance, namely sorbent type, number of extraction cycles (extract-discard) and elution volume, were evaluated. The optimal experimental conditions among those investigated for the quantification of U-LTB4 in urine samples were as follows: porous graphitic carbon sorbent (PGC), 10 extractions cycle (10×250 μL of sample) and LTB4 elution with 100 μL of acetonitrile. The UHPLC optimum conditions resulted in a mobile phase consisting of 95% (v/v) of acid aqueous solution (v/v), and acetonitrile 5% (v/v); flow rate of 500 µL/min, and a column temperature of 37±0.1 °C. Under optimized conditions the proposed method exhibit good selectivity and sensitivity LOD (0.37 ng/mL) and LOQ (1.22 ng/mL). The recovery ranging from 86.4 to 101.1% for LTB4, with relative standard deviations (% RSD) no larger than 5%. In addition, the method also afforded good results in terms of linearity (r(2)>0.995) within the established concentration range, with a residual deviation for each calibration point below 6%, and intra- and inter-day repeatability in urine samples with RSD values lower than 4 and 5%, respectively. The application of the method to urine samples revealed a tendency towards the increased urinary LTB4 levels in APs (5.42±0.17 ng/mL) when compared to those of CTRL group (from ND to 1.9 ng/mL). Urinary measurement of LTB4 may be an interesting and non-invasive option to assess control of asthma.

Evaluation of eicosanoids in nasal lavage as biomarkers of inflammation in patients with allergic rhinitis

INTRODUCTION

Cysteinyl leukotrienes (cys-LTs), 8-isoprostane and prostaglandin E2 (PGE2) constitute fundamental mediators in allergic inflammation; therefore we wanted to determine the utility of PGE2, 8-isoprostane and cys-LT levels in nasal lavage as biomarkers of allergic inflammation.

MATERIAL AND METHODS

Twenty-one patients with allergic rhinitis (AR) were included on the basis of a positive history of AR symptoms and positive results of skin prick tests to grass pollen allergens. The main exclusion criteria were: uncontrolled asthma, nasal polyps, respiratory infection, tuberculosis, neoplastic and autoimmune diseases, current smoking and immunotherapy. Both outside the pollen season and at the height of the pollen season, total nasal symptom score (TNS-4) was evaluated and the levels of cys-LTs, 8-isoprostane and PGE2 were measured in nasal lavage fluid (NALF).

RESULTS

Natural allergen stimulation resulted in a significant increase of TNS-4 (p < 0.001) and nasal eosinophilia (p < 0.001). The concentration of PGE2 dominated in the NALF outside the pollen season and decreased significantly at the height of natural exposure (p < 0.01). In contrast, lower baseline concentrations of cys-LTs and 8-isoprostane increased significantly upon allergen stimulation (p < 0.05). There was a significant correlation between mean concentration of PGE2 and eosinophil number in NALF (r = 0.67, p = 0.0439).

CONCLUSIONS

The NALF concentrations of cys-LTs and 8-isoprostane change simultaneously with TNS-4 and nasal eosinophilia. However, due to the lack of any significant correlation, their utility as markers of allergic rhinitis should be warily considered. The decrease of PGE2 concentration in NALF which correlated with nasal eosinophilia may participate in escalation of allergic inflammation and needs further evaluation.

Relationship between exhaled leukotriene and 8-isoprostane levels and asthma severity, asthma control level, and asthma control test score

OBJECTIVE

Exhaled breath condensate (EBC) is a completely non-invasive method for the collection of airway secretions to measure intense inflammation in the airways of asthmatics. It has been shown that the childhood asthma control test (c-ACT) is a good tool for use in the evaluation of asthmatics. Whether the c-ACT score and asthma control level correlate with the airway inflammation is not well known. We aimed to evaluate the relationship between exhaled cysteinyl leukotrienes (Cys-LTs) and 8-isoprostane levels and asthma severity, asthma control level and c-ACT score in asthmatic children.

METHODS

Thirty asthmatic children were evaluated with c-ACT score and pulmonary function tests. Asthma severity and asthma control level were assessed according to GINA. EBC was collected and Cys-LTs and 8-isoprostane concentrations were determined using a specific immunoassay kit.

RESULTS

Exhaled 8-isoprostane level in patients with moderate persistent asthma [114 (55-146)pg/ml] was higher than in the mild persistent group [52 (21-91)pg/ml] (p=0.05, Mann-Whitney U [MWU]). EBC 8-isoprostane in children with 1-4 asthma exacerbations/year [52 (16-80)pg/ml] was significantly lower than in children with >4 asthma exacerbations/year [114 (57-129)pg/ml] (p<0.05, MWU). No significant relation was determined between exhaled 8-isoprostane and Cys-LTs levels and c-ACT score and asthma control level. Exhaled 8-isoprostane correlated negatively with bronchodilator response (p=0.015, r=-0.45).

CONCLUSIONS

Exhaled 8-isoprostane, as an oxidative stress specifier, was found to be increased in relation with asthma exacerbation frequency and oxidative stress increases with the severity of asthma. In contrast to asthma severity level, c-ACT score and asthma control level may not reflect airway inflammation.

Non-invasive biomarkers in exacerbations of obstructive lung disease

BACKGROUND AND OBJECTIVE

Current methods of diagnosing exacerbations of asthma and chronic obstructive pulmonary disease (COPD) shed little light on their aetiology or pathophysiology. This study aimed to define the inflammatory biomarker profile of subjects with obstructive lung disease and to compare these with control subjects also with respiratory infections, using exhaled breath condensate (EBC) and induced sputum biomarker analysis.

METHODS

EBC, induced sputum and C-reactive protein were collected from subjects with exacerbations of asthma (n = 28), exacerbations of COPD (n = 29) and otherwise healthy controls with symptoms of respiratory tract infection (n = 28). Subjects were tested again after recovery. EBC and induced sputum were analysed for protein, hydrogen peroxide, interferon gamma inducible protein-10 (IP-10), neopterin, interleukin (IL)-6, IL-8, leukotriene B4 and tumour necrosis factor (TNF)-α. Sputum cell counts and EBC pH were also analysed.

RESULTS

EBC pH was significantly lower in exacerbation compared with recovery (5.54 0.07 vs 6.04 ± 0.08; P < 0.001). The novel markers IP-10 and neopterin were significantly increased in induced sputum supernatant (pooled groups pre and post exacerbation: IP-10: 188.6 ± 102.1 vs 5.40 ± 1.28 pg/mL, P = 0.006; neopterin: 15.81 ± 2.50 vs 5.38 ± 0.45 nmol/L, P < 0.0001), as was TNF-α (137.8 ± 49.64 vs 71.56 ± 45.03 pg/mL, P = 0.018). Few other biomarkers proved significantly different in exacerbation, although C-reactive protein was raised.

CONCLUSIONS

Non-invasive biomarker assessment may provide useful information in exacerbation of obstructive lung diseases, particularly sputum IP-10 and neopterin and EBC pH.

Using high-performance liquid chromatography with UV detector to quantify exhaled leukotriene B4 level in nonatopic adults

This study aimed to evaluate the feasibility of the chemical method to analyze exhaled breath condensate (EBC) leukotriene B4 (LTB4) level in humans. High-performance liquid chromatography with a UV detector was applied to quantify the inflammatory biomarker. The LTB4 concentration in the concentrated pooled EBC samples was 1.19 ng/μL, and the average LTB4 concentration of each EBC sample was 15.38 ng/μL. This analytical technique was feasible to evaluate the levels of inflammatory mediators such as LTB4 in human EBCs without any complicated sample pretreatment processes.

Breath tests in respiratory and critical care medicine: from research to practice in current perspectives

Today, exhaled nitric oxide has been studied the most, and most researches have now focused on asthma. More than a thousand different volatile organic compounds have been observed in low concentrations in normal human breath. Alkanes and methylalkanes, the majority of breath volatile organic compounds, have been increasingly used by physicians as a novel method to diagnose many diseases without discomforts of invasive procedures. None of the individual exhaled volatile organic compound alone is specific for disease. Exhaled breath analysis techniques may be available to diagnose and monitor the diseases in home setting when their sensitivity and specificity are improved in the future.

Application of metabolomics approaches to the study of respiratory diseases

Metabolomics is the global unbiased analysis of all the small-molecule metabolites within a biological system, under a given set of conditions. These methods offer the potential for a holistic approach to clinical medicine, as well as improving disease diagnosis and understanding of pathological mechanisms. Respiratory diseases including asthma and chronic obstructive pulmonary disorder are increasing globally, with the latter predicted to become the third leading cause of global mortality by 2020. The root causes for disease onset remain poorly understood and no cures are available. This review presents an overview of metabolomics followed by in-depth discussion of its application to the study of respiratory diseases, including the design of metabolomics experiments, choice of clinical material collected and potentially confounding experimental factors. Particular challenges in the field are presented and placed within the context of the future of the applications of metabolomics approaches to the study of respiratory diseases.

Classification of odorants in the vapor phase using composite features for a portable e-nose system

We present an effective portable e-nose system that performs well even in noisy environments. Considering the characteristics of the e-nose data, we use an image covariance matrix-based method for extracting discriminant features for vapor classification. To construct composite vectors, primitive variables of the data measured by a sensor array are rearranged. Then, composite features are extracted by utilizing the information about the statistical dependency among multiple primitive variables, and a classifier for vapor classification is designed with these composite features. Experimental results with different volatile organic compounds data show that the proposed system has better classification performance than other methods in a noisy environment.

Exhaled breath condensate pH in patients with cystic fibrosis

OBJECTIVE AND DESIGN

Exhaled breath condensate (EBC) pH has been proposed as a useful, non-invasive marker of airway inflammation in pulmonary diseases. In this study we tested whether cystic fibrosis (CF) is associated with acidification of EBC, when pH is assessed by the CO(2) gas standardization method.

METHODS

EBC was collected using two different devices (EcoScreen and R-Tube) in 46 stable CF patients during routine clinical visits and in 28 healthy controls.

RESULTS

Mean EBC pH in CF patients and in healthy controls was similar (EcoScreen: CF patients: 6.38 ± 0.03 versus controls: 6.39 ± 0.03, p = 0.699; R-tube: CF patients: 5.94 ± 0.04 versus controls: 6.02 ± 0.03, p = 0.159). Inflammatory cell counts in spontaneously expectorated sputum obtained in a subset of patients (n = 20) showed no correlation with pH values. EBC samples collected with the R-tube were more acidic than those collected with the EcoScreen device (p < 0.001).

CONCLUSIONS

Our data suggest that EBC pH does not discriminate between healthy controls and those with CF disease indicating that the clinical applicability of EBC pH measurements for assessing airway inflammation in CF is limited.

Smart sensor systems for human health breath monitoring applications

Breath analysis techniques offer a potential revolution in health care diagnostics, especially if these techniques can be brought into standard use in the clinic and at home. The advent of microsensors combined with smart sensor system technology enables a new generation of sensor systems with significantly enhanced capabilities and minimal size, weight and power consumption. This paper discusses the microsensor/smart sensor system approach and provides a summary of efforts to migrate this technology into human health breath monitoring applications. First, the basic capability of this approach to measure exhaled breath associated with exercise physiology is demonstrated. Building from this foundation, the development of a system for a portable asthma home health care system is described. A solid-state nitric oxide (NO) sensor for asthma monitoring has been identified, and efforts are underway to miniaturize this NO sensor technology and integrate it into a smart sensor system. It is concluded that base platform microsensor technology combined with smart sensor systems can address the needs of a range of breath monitoring applications and enable new capabilities for healthcare.

Demonstration that methadone is being present in the exhaled breath aerosol fraction

Methadone has previously been found present in exhaled breath of methadone treated patients. This study aimed at studying if methadone is present in the aerosol fraction of exhaled breath and used different filter sampling techniques for that. Patients receiving methadone maintenance treatment were recruited for the study. Methadone was extracted from filters collecting methadone from exhaled breath using 2-propanol, methanol and ethyl acetate and measured using liquid-chromatography-tandem mass-spectrometry. The limit of quantification was 5 pg/sample and the intra-day imprecision and accuracy within 15%. The recovery of extracting methadone from filters was >90%. Two types of micro-particle filters were used in this study and were compared with the C18 silica filter (Empore) used before. The Glass fiber filter collected methadone from exhaled breath of methadone patients. The amount collected significantly exceeded the amount using the C18 Empore filter (3.6-14-fold), but the variability of amount trapped was large. The second filter type was a polymer filter. Also this filter was able to trap methadone from exhaled breath of methadone patients. The amount and variability was similar to the C18 Empore filter but smaller than the Glass fiber filter. The mean rate of methadone excretion measured with the best polymer filter was 92 pg/min with a range between 20 and 287 (n=5). The polymer filter has the practical advantage of having a low flow resistance making it possible to sample without pumping assistance. The polymer filter was found to collect >90% of the exhaled methadone. The conclusion of this study was that methadone in exhaled breath is carried in the aerosol fraction known to be formed in the lung as a result of normal breathing.

Sputum and nasal lavage lung-specific biomarkers before and after smoking cessation

Background

Little is known about the effect of smoking cessation on airway inflammation. Secretory Leukocyte Protease Inhibitor (SLPI), Clara Cell protein 16 (CC16), elafin and human defensin beta-2 (HBD-2) protect human airways against inflammation and oxidative stress. In this longitudinal study we aimed to investigate changes in sputum and nasal lavage SLPI, CC16, elafin and HBD-2 levels in healthy smokers after 6 and 12 months of smoking cessation.

Methods

Induced sputum and nasal lavage was obtained from healthy current smokers (n = 76) before smoking cessation, after 6 months of smoking cessation (n = 29), after 1 year of smoking cessation (n = 22) and from 10 healthy never smokers. SLPI, CC16, elafin and HBD-2 levels were measured in sputum and nasal lavage supernatants by commercially available ELISA kits.

Results

Sputum SLPI and CC-16 levels were increased in healthy smokers before smoking cessation versus never-smokers (p = 0.005 and p = 0.08 respectively). SLPI and CC16 levels did not differ before and 6 months after smoking cessation (p = 0.118 and p = 0.543 respectively), neither before and 1 year after smoking cessation (p = 0.363 and p = 0.470 respectively). Nasal lavage SLPI was decreased 12 months after smoking cessation (p = 0.033). Nasal lavage elafin levels were increased in healthy smokers before smoking cessation versus never-smokers (p = 0.007), but there were no changes 6 months and 1 year after smoking cessation.

Conclusions

Only nasal lavage SLPI decrease after 1 year after smoking cessation. We may speculate that there is an ongoing inflammatory process stimulating the production of counter-regulating proteins in the airways of healthy ex-smokers.

Hydrogen peroxide in exhaled breath condensate in patients with asthma: a promising biomarker?

BACKGROUND

The measurement of hydrogen peroxide (H(2)O(2)) in exhaled breath condensate (EBC) has been proposed as a noninvasive way of monitoring airway inflammation. However, results from individual studies on EBC H(2)O(2) evaluation of asthma are conflicting. The purpose of this study was to explore whether EBC H(2)O(2) is elevated in people with asthma and whether it reflects disease severity and disease control or responds to corticosteroid treatment.

METHODS

Studies were identified by searching PubMed, Embase, Cochrane Database, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and www.controlled-trials.com for relevant reports published before September 2010. Observational studies comparing levels of EBC H(2)O(2) between patients with asthma who were nonsmokers and healthy subjects were included. Data were independently extracted by two investigators and analyzed using Stata 10.0 software.

RESULTS

Eight studies (involving 728 participants) were included. EBC H(2)O(2) concentrations were significantly higher in patients with asthma who were nonsmokers compared with healthy subjects, and higher values of EBC H(2)O(2) were observed at each level of asthma, classified either by severity or control level, and the values were negatively correlated with FEV(1). In addition, EBC H(2)O(2) concentrations were lower in patients with asthma treated with corticosteroids than in patients with asthma not treated with corticosteroids.

CONCLUSIONS

H(2)O(2) might be a promising biomarker for guiding asthma treatment. However, further investigation is needed to establish its role.

A new approach to study exhaled proteins as potential biomarkers for asthma

BACKGROUND

Asthma is a complex clinical disease characterized by airway inflammation. Recently, various studies reported on the analysis of exhaled breath condensate (EBC) in the search for potential biomarkers for asthma. However, in a complex disease such as asthma, one biomarker might not be enough for early diagnosis or follow-up.

OBJECTIVE

The use of proteome analysis may reveal disease-specific proteolytic peptide or protein patterns, and may lead to the identification of novel proteins for the detection of asthma.

METHODS

Liquid chromatography and mass spectrometry were used to separate and detect proteins (proteolytic peptides) present in EBC samples from 30 healthy children and 40 children with asthma in the age group of 6-12 years.

RESULTS

Support vector machine analysis resulted in differentiating profiles based on asthma status. These proteolytic peptide patterns were not correlated to some well known (spirometry, exhaled nitric oxide) and more recently described exhaled markers (EBC pH, LTB₄). The more abundant proteins in EBC were identified as cytokeratins, albumin, actin, haemoglobin, lysozyme, dermcidin, and calgranulin B.

CONCLUSION

Although the exact role in the disease development or physiological state of the airways of the proteins described in the presented pattern is not clear at this moment, this is an important step in the search for exhaled biomarkers for asthma. This study shows that EBC contains proteins that are of interest for future non-invasive asthma diagnosis or follow-up.

Effects of a short-term rehabilitation program on airway inflammation in children with cystic fibrosis

BACKGROUND

Respiratory therapy in cystic fibrosis (CF) consists of airway clearance, infection control, and reduction of airway inflammation. It is well recognized that physical activity as well as daily chest physiotherapy, enhance airway clearance. We investigated the effects of pulmonary rehabilitation, including physical activity and chest physiotherapy, on airway inflammation in children with CF.

METHODS

Eighteen children with stable CF (six females), aged 8.2-16.2 years, participating in a 3-week multidisciplinary inpatient rehabilitation program were recruited. Assessment at the beginning and the end of the program included clinical score, pulmonary function test, exhaled breath condensate (EBC) and sputum analysis. Sputum supernatant and EBC were analyzed for interleukin (IL)-1b, 6, 8, 10, 12, tumor necrosis factor-alpha (TNF-alpha) and LTB4.

RESULTS

Median (IQR) symptom scores decreased from 19 [23] to 16 [21], P = 0.005. Vital capacity and FVC increased significantly (P < 0.05). However no difference was found for the total sputum cells and sputum as well as EBC cytokines between the two visits. Significant correlations were found for sputum IL-1 (+), IL-6 (-), and IL-8 (+) to total sputum cell count and neutrophils and for IL-8 to TNF-alpha.

CONCLUSIONS

We have shown that a short-term inpatient rehabilitation for children with stable CF with intensive physical activity mainly improve subjective clinical symptoms and measures of lung function such as VC and FVC but does not influence airflow obstruction and airway inflammation as assessed by sputum and EBC analysis.

Exhaled nitric oxide and other major exhaled compounds for the diagnosis of metabolic diseases

BACKGROUND

Many metabolic diseases including obesity, cardiovascular disease and diabetes share common pathogenetic pathways, which may involve chronic oxidative stress and inflammation. There is increasing evidence that assessment of biomarkers on exhaled gases or exhaled breath condensate may serve as a non-invasive tool to detect abnormalities in metabolic diseases mirroring increased in oxidative stress, systemic inflammation and endothelial dysfunction.

METHODS

Among commonly used exhaled biomarkers, nitric oxide (NO) on exhaled air and some constituents of exhaled breath condensate in volatile or non-volatile form may represent suitable markers. Nasal, bronchial and alveolar NO could be analyzed separately, with implications in the assessment of systemic disease and endothelial dysfunction. Moreover, the profiles of several exhaled gases have a place in phenotyping diabetic patients and their risk of complications. Accordingly, metabolomics of the airway fluid using exhaled breath condensate has recently confirmed the value of this biological matrix for the evaluation of both volatile and non-volatile biomarkers.

CONCLUSION

Normative studies for reference values are, however, lacking, and the influence of preanalytical variables on the methodology warrants further studies.

Analysis of exhaled breath condensate in respiratory medicine: methodological aspects and potential clinical applications

Analysis of exhaled breath condensate (EBC) is a noninvasive method for studying the composition of airway lining fluid and has the potential for assessing lung inflammation. EBC is mainly formed by water vapor, but also contains aerosol particles in which several biomolecules including leukotrienes, 8-isoprostane, prostaglandins, hydrogen peroxide, nitric oxide-derived products, and hydrogen ions, have been detected in healthy subjects. Inflammatory mediators in EBC are detected in healthy subjects and some of them are elevated in patients with different lung diseases. Analysis of EBC is completely noninvasive, is particularly suitable for longitudinal studies, and is potentially useful for assessing the response to pharmacological therapy. Identification of selective profiles of biomarkers of lung diseases might also have a diagnostic value. However, EBC analysis currently has important limitations. The lack of standardized procedures for EBC analysis and validation of some analytical techniques makes it difficult comparison of results from different laboratories. Analysis of EBC is currently more useful for relative measures than for quantitative assessment of inflammatory mediators. Reference analytical techniques are required to provide definitive evidence for the presence of some inflammatory mediators in EBC and for their accurate quantitative assessment in this biological fluid. Several methodological issues need to be addressed before EBC analysis can be considered for clinical applications. However, further research in this area is warranted due to the relative lack of noninvasive methods for assessing lung inflammation.

Exhaled leukotriene B4 in children with community acquired pneumonia

BACKGROUND

The infiltrate in pneumonia is characterized by a large number of activated neutrophils, for which leukotriene B4 (LTB4) is a strong chemotactic agent. Exhaled breath condensate (EBC) is a non-invasive technique for studying the lower airways. The present study was conducted to measure EBC LTB4 as a potential non-invasive marker of inflammatory response in community acquired pneumonia (CAP).

METHODS

Eighteen children with CAP and 17 healthy children were recruited (age 5-13). The CAP children underwent physical examination, chest X-ray, leukocyte count and C-reactive protein measurement. The CAP and the control children performed spirometry, exhaled nitric oxide measurement (FE(NO)) and EBC collection for LTB4 assessment. In the CAP children spirometry, FE(NO) and EBC collection were repeated twice over a 1-month follow-up.

RESULTS

LTB4 EBC concentrations were higher in children with CAP than in healthy controls (10 pg/ml [7.0-15.3] vs. 3 pg/ml [3.0-6.9], P = 0.001) and decreased after 1 week (3 pg/ml [3.0-7.2], P < 0.01) with no further change a month later. In the acute phase spirometry demonstrated a restrictive pattern that gradually improved later. No difference in FE(NO) levels was found between children with CAP and healthy controls.

CONCLUSION

Exhaled LTB4 levels increase in CAP and return to normal after 1 week. EBC collection is feasible in children with CAP and may represent a new way to non-invasively monitor the lung's biological response to infections.

Biomarkers in exhaled breath condensate: a review of collection, processing and analysis

Exhaled breath condensate (EBC) is a potential rich source for countless biomarkers that can provide valuable information about respiratory as well as systemic diseases. EBC has been studied in a variety of diseases including allergic rhinitis, asthma, chronic obstructive lung disease, cystic fibrosis, lung cancer, and obstructive sleep apnea syndrome. Although numerous biomarkers have been discovered and studied in EBC, the methods of collection and biomarker detection have not been fully standardized. While leaving standardization methods up to individual labs for the present time is optimal for the continued discovery of new biomarkers in EBC, this decreases the reproducibility and generalizability of the findings. In this review we will discuss specific biomarkers studied in specific diseases as well as some of the related technical issues including collection, processing and analysis.

Exhaled breath condensate: a new method for lung disease diagnosis

Analysis of exhaled breath composition in lung disease patients can indirectly point to biochemical changes that occur in the fluid lining airway surfaces. The parameters of redox and acid-base changes, and of inflammatory changes relevant in the pathogenesis of most pulmonary diseases are currently most widely determined in exhaled breath condensate. The collection of exhaled breath condensate is a safe, non-invasive, easy and simple diagnostic procedure that is suitable for longitudinal studies and applicable in patients of all age groups, irrespective of the disease severity. In spite of many scientific studies involving lung disease patients, methodology for exhaled breath condensate collection and analysis has not yet been realized for daily utilization. Additional studies of the exact origin of condensate constituents and standardization of the overall analytical process, including collection, storage, analysis and result interpretation, are needed. Irrespective of these limitations, further investigation of this sample type is fully justified by the fact that classical specimens used in the management of pulmonary disease are either obtained by invasive procedures (e.g., induced sputum, biopsy, bronchoalveolar lavage) or cannot provide appropriate information (e.g., urine, serum). Analysis of exhaled breath condensate in the future might contribute significantly to our understanding of the physiological and pathophysiological processes in lungs, to early detection, diagnosis and follow up of disease progression, and to evaluation of therapeutic response.

Collection of exhaled breath and exhaled breath condensate in veterinary medicine. A review

Collection of exhaled breath (EB) and exhaled breath condensate (EBC) is a noninvasive method for obtaining samples from the lower airways. While this technique has been well established for the diagnosis of lower respiratory tract diseases in human medicine, only a few studies have been performed in veterinary medicine. This article critically reviews the collection methods and parameter values measured in various animal species published to date and points out directions for further research.

Method optimization and validation for the simultaneous determination of arachidonic acid metabolites in exhaled breath condensate by liquid chromatography-electrospray ionization tandem mass spectrometry

Background

Determinations of inflammatory markers in exhaled breath condensate were used to assess airway inflammation. The most applied method for this kind of determination is enzyme immunoassay. For research purposes to find new or to relate concrete biomarkers to different pulmonary diseases, a simultaneous determination of different inflammatory markers would be advantageous.

Methods

We developed an analytical method with on-line clean up and enrichment steps to determine 12 different inflammatory markers in exhaled breath condensate. A specific detection method ensures the unequivocally determination of each analyte at the same run. The method was optimized and validated to achieve a low limit of quantification up to 10 pg/mL each analyte. The precision of the method ranged between 4 and 16%.

Conclusion

The presented method should serve as an easy and fast tool to assess the utility of inflammatory markers in exhaled breath condensate to different pulmonary diseases and for several related disciplines in medicine.

Pulmonary biomarkers in chronic obstructive pulmonary disease

There has been increasing interest in using pulmonary biomarkers to understand and monitor the inflammation in the respiratory tract of patients with chronic obstructive pulmonary disease (COPD). In this Pulmonary Perspective we discuss the merits of the various approaches by reviewing the current literature on pulmonary biomarkers in COPD and underscore the need for more systematic studies in the future. Bronchial biopsies and bronchoalveolar lavage provide valuable information about inflammatory cells and mediators, but are invasive, so that repeated measurements have to be very limited in assessing any interventions. Induced sputum has provided considerable information about the inflammatory process, including mediators and proteinases in COPD, but selectively samples proximal airways and may not closely reflect distal inflammatory processes. Exhaled gases and breath condensate are noninvasive procedures, so repeated measurements are possible, but for some assays the variability is relatively high. There is relatively little information about how any of these biomarkers relate to other clinical outcomes, such as progression of the disease, severity of disease, clinical subtypes, or response to therapy. More information is also needed about the variability in these measurements. In the future, pulmonary biomarkers may be useful in predicting disease progression, indicating disease instability, and in predicting response to current therapies and novel therapies, many of which are now in development.

Biomarkers of neutrophilic inflammation in exhaled air of cystic fibrosis children with bacterial airway infections

Leukotriene B(4) (LTB(4)) and interleukin-8 (IL-8) are inflammatory mediators involved in the neutrophil response to pulmonary bacterial colonization in cystic fibrosis (CF). The aim of this study was to investigate whether the LTB(4) and IL-8 levels in exhaled breath condensate (EBC) could be related to the type of bacterial colonization in CF patients. The pH level in EBC was analyzed as an estimate of airway acidification. Forty children were evaluated: 10 CF patients with P. aeruginosa, 10 CF patients with S. aureus, 10 not colonized CF patients, and 10 healthy children. LTB(4) and IL-8 in EBC were analyzed by specific enzyme immunoassay kits (EIA). The pH of EBC was measured with a pH-meter after deareation by bubbling with argon. Exhaled LTB(4) was higher in CF children with P. aeruginosa compared to those with S. aureus (P < 0.01), not colonized (P < 0.001), and healthy children (P < 0.01). Exhaled IL-8 was elevated in CF patients colonized by P. aeruginosa compared with other subgroups (vs. not colonized, P < 0.05; vs. healthy children, P < 0.001). IL-8 levels were higher in CF children with S. aureus than in healthy children (P < 0.05). There was an increase in IL-8 levels in not colonized CF patients compared with healthy children (P < 0.05). EBC pH was higher in healthy children compared to CF patients not colonized (P < 0.05). Our data suggest that EBC is suitable for evaluating neutrophil inflammatory mediators (LTB(4), IL-8, and pH) involved in the response to pulmonary bacterial colonization in CF children.

Effects of cyclo-oxygenase inhibition on exhaled eicosanoids in patients with COPD

BACKGROUND

Leukotriene (LT) B4 concentrations are increased and prostaglandin (PG) E2 concentrations are decreased in exhaled breath condensate (EBC) in patients with chronic obstructive pulmonary disease (COPD). A study was undertaken to investigate the short term effects of cyclo-oxygenase (COX) inhibition on exhaled LTB4 and PGE2 concentrations in patients with COPD and to identify the COX isoform responsible for exhaled PGE2 production.

METHODS

Two studies were performed. A double blind, crossover, randomised, placebo controlled study with ibuprofen (400 mg qid for 2 days), a non-selective COX inhibitor, was undertaken in 14 patients with stable COPD, and an open label study with oral rofecoxib (25 mg once a day for 5 days), a selective COX-2 inhibitor, was undertaken in a different group of 16 COPD patients. EBC was collected before and after drug treatment. Exhaled LTB4 and PGE2 concentrations were measured with specific immunoassays.

RESULTS

All patients complied with treatment as indicated by a reduction in ex vivo serum thromboxane B2 concentrations (ibuprofen) and a reduction in lipopolysaccharide induced increase in ex vivo plasma PGE2 values (rofecoxib) of more than 80%. Exhaled LTB4 was increased after ibuprofen (median 175.5 (interquartile range 128.8-231.5) pg/ml v 84.0 (70.0-98.5) pg/ml, p < 0.001) and exhaled PGE2 was reduced (93.5 (84.0-105-5) pg/ml v 22.0 (15.0-25.5) pg/ml, p < 0.0001). Rofecoxib had no effect on exhaled LTB4 (p = 0.53) or PGE2 (p = 0.23).

CONCLUSIONS

Non-selective COX inhibition decreases PGE2 and increases LTB4 in EBC, whereas selective COX-2 inhibition has no effect on these eicosanoids. PGE2 in EBC is primarily derived from COX-1 activity, and COX inhibition may redirect arachidonic acid metabolism towards the 5-lipoxygenase pathway.

Exhaled breath condensate eicosanoids and sputum eosinophils in asthmatic children: a pilot study

Cysteinyl leukotrienes (cys-LTs), LTB4 and 8-isoprostane are increased in the exhaled breath condensate (EBC) from asthmatic patients. The aim of this study was to investigate whether the measurement of cys-LTs, LTB4 and 8-isoprostane in EBC can reflect the level of airway inflammation assessed by induced sputum in asthmatic children sensitized to house dust mite (HDM) during natural avoidance of HDM allergens. Twelve children were evaluated at the time of admission (T0) and after 3 months of stay (T1) at the Istituto Pio XII (Misurina, Italian Dolomites 1756 m). Sputum eosinophil percentage and measurement of cys-LTs, LTB4 and 8-isoprostanes in the breath condensate at T0 and T1 were evaluated. Eosinophil percentage in induced sputum was 8.5 +/- 1.1% at T0 and 3.5 +/- 0.4% at T1 (p = 0.011). Neutrophil percentage in sputum was 1.1 +/- 0.5% at T0 and 1.5 +/- 1.0% at T1 (ns). Cys-LTs mean level was 14.24 +/- 4.53 pg/ml at T0 and 4.65 +/- 0.68 pg/ml at T1 (p = 0.0125). LTB4 level was 2.36 +/- 0.19 pg/ml at T0 and 2.41 +/- 0.23 pg/ml at T1 (ns). 8-Isoprostane level reduced from 17.47 +/- 3.18 pg/ml at T0 to 7.36 +/- 3.26 pg/ml at T1 (p = 0.003). This study show that exhaled cys-LTs and 8-isoprostane, as well as eosinophil percentage in induced sputum, are reduced after allergen avoidance in asthmatic children suggesting a potential application of EBC for the non-invasive evaluation of airway inflammation in asthma in allergic asthmatic children.

Ion trap liquid chromatography/tandem mass spectrometry analysis of leukotriene B4 in exhaled breath condensate

The objective of this study is the measurement of leukotriene B7 (LTB4), a potent inflammatory mediator, in exhaled breath condensate by using liquid chromatography/mass spectrometry (LC/MS and LC/MS/MS). Condensation of exhaled breath is a non-invasive method to collect airway secretions. Deuterated (d4)-LTB4 was used as internal standard. The MS and MS/MS behavior of LTB4 and LTB4-d4 was studied by electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) in both positive and negative ion polarity mode. Preliminary results show that monitoring negative ions in ESI mode has the best sensitivity for both LTB4 and LTB4-d4. Therefore, negative ESI was chosen, and the [M-H]- ions at m/z 335 and 339 were selected for quantification. The lower limit of quantification for LTB4, expressed as the lowest point of the calibration curve, was 100 pg/mL. Using this technique, we measured LTB4 in exhaled breath condensate in two healthy subjects, four asthmatic patients on anti-inflammatory treatment, and four asthmatic patients who were not on anti-inflammatory drugs. Exhaled LTB4 concentrations were detected only in asthmatic patients who were not on anti-inflammatory therapy. This method is potentially useful for non-invasive assessment of airway inflammation, but the sensitivity of the technique needs to be improved.

Exhaled leukotrienes and prostaglandins in COPD

BACKGROUND

The role of eicosanoids, including leukotrienes (LTs) and prostaglandins (PGs), in chronic obstructive pulmonary disease (COPD) is uncertain. The aim of this study was to investigate whether eicosanoids are measurable in exhaled breath condensate (EBC), a non-invasive method of collecting airway secretions, in patients with stable mild to moderate COPD, and to show possible differences in their concentrations compared with control subjects.

METHODS

LTB(4), LTE(4), PGE(2), PGD(2)-methoxime, PGF(2alpha), and thromboxane B(2) (TxB(2)) were measured in EBC in 15 healthy ex-smokers, 20 steroid naïve patients with COPD who were ex-smokers, and in 25 patients with COPD who were ex-smokers and who were treated with inhaled corticosteroids. The study was of cross sectional design and all subjects were matched for age and smoking habit.

RESULTS

LTB(4) and PGE(2) concentrations were increased in steroid naïve (LTB(4): median 100.6 (range 73.5-145.0) pg/ml, p<0.001; PGE(2): 98.0 (range 57.0-128.4) pg/ml, p<0.001) and steroid treated patients with COPD (LTB(4): 99.0 (range 57.9-170.5) pg/ml, p<0.001; PGE(2): 93.6 (range 52.8-157.0) pg/ml, p<0.001) compared with control subjects (LTB(4): 38.1 (range 31.2-53.6) pg/ml; PGE(2): 44.3 (range 30.2-52.1) pg/ml). Both groups of patients had similar concentrations of exhaled LTB(4) (p=0.43) and PGE(2) (p=0.59). When measurable, LTE(4) and PGD(2)-methoxime concentrations were similar in COPD patients and controls, whereas PGF(2alpha) concentrations were increased in the former. TxB(2)-LI was undetectable in any of the subjects.

CONCLUSIONS

There is a selective increase in exhaled LTB(4) and PGE(2) in patients with COPD which may be relatively resistant to inhaled corticosteroid therapy.