Exhaled volatile organic compounds and lung microbiome in COPD: a pilot randomised controlled trial

Breath biopsy in inborn errors of metabolism: A proof-of-principle study in propionic acidemia

BACKGROUND

Impaired oxidation of branched chain amino acids may give rise to volatile organic compounds (VOCs). We hypothesized that VOCs will be present in exhaled breath of participants with propionic acidemia (PA), and their relative abundance would correlate with clinical and biochemical characteristics of the disease.

METHODS

We enrolled 5 affected participants from a natural history study of PA (ClinicalTrials.gov ID NCT02890342) plus five age- and sex-matched unaffected controls. We collected exhaled breath using a non-invasive breath sampling platform paired with thermal desorption-gas chromatography-mass spectrometry. Clinical and biochemical parameters were correlated with the relative abundance of VOCs.

RESULTS

Unbiased screening identified several candidate VOC biomarkers of PA. One candidate putatively identified as 3-pentanone was the most abundant (45-fold higher in cases vs. controls, p-value <0.05). 3-Pentanone abundance positively correlated with plasma propionylcarnitine (p = 0.01), plasma 2-methylcitrate (p < 0.05), 3-OH-propionate (p < 0.01), full scale IQ (p < 0.01), and showed a statistical trend with height z-scores (p = 0.08). It inversely correlated with the whole-body in vivo oxidation of 1-13C-propionate (p < 0.05). In a participant who received an orthotopic liver transplant, 3-pentanone levels were lower and segregated with "mild" PA.

CONCLUSION

Non-invasive breath sampling is a promising method to identify and quantitate VOCs that correlate with the clinical and biochemical parameters of PA. Our proof-of-principle findings may have wide implications for the diagnosis and severity stratification of inborn errors of metabolism affecting oxidation of amino acids which might be monitored in a similar fashion.

SYNOPSIS

A proof-of-principle study putatively identifies 3-pentanone in exhaled breath as a correlate of the clinical and biochemical outcomes in propionic acidemia.

Exhaled Volatile Organic Compounds for Asthma Control Classification in Children with Moderate to Severe Asthma: Results from the SysPharmPediA Study

Rationale: The early identification of children with poorly controlled asthma is imperative for optimizing treatment strategies. The analysis of exhaled volatile organic compounds (VOCs) is an emerging approach to identify prognostic and diagnostic biomarkers in pediatric asthma. Objectives: To assess the accuracy of gas chromatography-mass spectrometry-based exhaled metabolite analysis to differentiate between controlled and uncontrolled pediatric asthma. Methods: This study encompassed discovery (SysPharmPediA [Systems Pharmacology Approach to Uncontrolled Paediatric Asthma]) and validation (U-BIOPRED [Unbiased Biomarkers for the Prediction of Respiratory Disease Outcomes] and PANDA [Paediatric-Asthma-Non-Invasive-Diagnostic-Approaches]) phases. First, exhaled VOCs that discriminated degrees of asthma control were identified. Subsequently, outcomes were validated in two independent cohorts. Patients were classified as controlled or uncontrolled on the basis of asthma control test scores and the number of severe attacks in the past year. In addition, the potential of VOCs to predict two or more future severe asthma attacks in SysPharmPediA was evaluated. Measurements and Main Results: Complete data were available for 196 children (SysPharmPediA, n = 100; U-BIOPRED, n = 49; PANDA, n = 47). In SysPharmPediA, after randomly splitting the population into training (n = 51) and test (n = 49) sets, three compounds (acetophenone, ethylbenzene, and styrene) distinguished between patients with uncontrolled and controlled asthma. The areas under the receiver operating characteristic curves (AUROCCs) for training and test sets were, respectively, 0.83 (95% confidence interval [CI], 0.65-1.00) and 0.77 (95% CI, 0.58-0.96). Combinations of these VOCs resulted in AUROCCs of 0.74 ± 0.06 (U-BIOPRED) and 0.68 ± 0.05 (PANDA). Attack prediction tests resulted in AUROCCs of 0.71 (95% CI, 0.51-0.91) and 0.71 (95% CI, 0.52-0.90) for the training and test sets. Conclusions: Exhaled metabolite analysis might enable asthma control classification in children. This should stimulate the further development of exhaled metabolite-based point-of-care tests in asthma.

New methods to detect bacterial or viral infections in patients with chronic obstructive pulmonary disease

INTRODUCTION

Patients with chronic obstructive pulmonary disease (COPD) are frequently colonized and infected by respiratory pathogens. Identifying these infectious etiologies is critical for understanding the microbial dynamics of COPD and for the appropriate use of antimicrobials during exacerbations.

AREAS COVERED

Traditional methods, such as bacterial and viral cultures, have been standard in diagnosing respiratory infections. However, these methods have significant limitations, including lack of sensitivity and prolonged turnaround time. Modern molecular approaches offer rapid, sensitive, and specific detection, though they also come with their own challenges. This review explores and evaluates the clinical utility of the latest advancements in detecting bacterial and viral respiratory infections in COPD, encompassing molecular techniques, biomarkers, and emerging technologies.

EXPERT OPINION

In the evolving landscape of COPD management, integrating molecular diagnostics and emerging technologies holds great promise. The enhanced sensitivity of molecular techniques has significantly advanced our understanding of the role of microbes in COPD. However, many of these technologies have primarily been developed for pneumonia diagnosis or research applications, and their clinical utility in managing COPD requires further evaluation.

Assessing volatile organic compounds exposure and chronic obstructive pulmonary diseases in US adults

Background

Volatile organic compounds (VOCs) are a large group of chemicals widely used in People's Daily life. There is increasing evidence of the cumulative toxicity of VOCs. However, the association between VOCs and the risk of COPD has not been reported.

Objective

We comprehensively evaluated the association between VOCs and COPD.

Methods

Our study included a total of 1,477 subjects from the National Health and Nutrition Examination Survey, including VOCs, COPD, and other variables in the average US population. Multiple regression models and smooth-curve fitting (penalty splines) were constructed to examine potential associations, and stratified analyses were used to identify high-risk groups.

Results

We found a positive association between blood benzene and blood o-xylene concentrations and COPD risk and identified a concentration relationship between the two. That is, when the blood benzene and O-xylene concentrations reached 0.28 ng/mL and 0.08 ng/mL, respectively, the risk of COPD was the highest. In addition, we found that gender, age, and MET influence the relationship, especially in women, young people, and people with low MET.

Significance

This study revealed that blood benzene and blood o-xylene were independently and positively correlated with COPD risk, suggesting that long-term exposure to benzene and O-xylene may cause pulmonary diseases, and providing a new standard of related blood VOCs concentration for the prevention of COPD.

New drugs under development for COPD

The characteristic features of chronic obstructive pulmonary disease (COPD) include inflammation and remodelling of the lower airways and lung parenchyma together with activation of inflammatory and immune processes. Due to the increasing habit of cigarette smoking worldwide COPD prevalence is increasing globally. Current therapies are unable to prevent COPD progression in many patients or target many of its hallmark characteristics which may reflect the lack of adequate biomarkers to detect the heterogeneous clinical and molecular nature of COPD. In this chapter we review recent molecular data that may indicate novel pathways that underpin COPD subphenotypes and indicate potential improvements in the classes of drugs currently used to treat COPD. We also highlight the evidence for new drugs or approaches to treat COPD identified using molecular and other approaches including kinase inhibitors, cytokine- and chemokine-directed biologicals and small molecules, antioxidants and redox signalling pathway inhibitors, inhaled anti-infectious agents and senolytics. It is important to consider the phenotypes/molecular endotypes of COPD patients together with specific outcome measures to target new therapies to particular COPD subtypes. This will require greater understanding of COPD molecular pathologies and a focus on biomarkers of predicting disease subsets and responder/non-responder populations.

Breath-Taking Perspectives and Preliminary Data toward Early Detection of Chronic Liver Diseases

The gold standard method for chronic liver diseases diagnosis and staging remains liver biopsy, despite the spread of less invasive surrogate modalities based on imaging and blood biomarkers. Still, more than 50% of chronic liver disease cases are detected at later stages when patients exhibit episodes of liver decompensation. Breath analysis represents an attractive means for the development of non-invasive tests for several pathologies, including chronic liver diseases. In this perspective review, we summarize the main findings of studies that compared the breath of patients with chronic liver diseases against that of control subjects and found candidate biomarkers for a potential breath test. Interestingly, identified compounds with best classification performance are of exogenous origin and used as flavoring agents in food. Therefore, random dietary exposure of the general population to these compounds prevents the establishment of threshold levels for the identification of disease subjects. To overcome this limitation, we propose the exogenous volatile organic compounds (EVOCs) probe approach, where one or multiple of these flavoring agent(s) are administered at a standard dose and liver dysfunction associated with chronic liver diseases is evaluated as a washout of ingested compound(s). We report preliminary results in healthy subjects in support of the potential of the EVOC Probe approach.