Detection ofClostridioides difficileinfection by assessment of exhaled breath volatile organic compounds

Clostridioides difficileinfection (CDI) is the leading cause of hospital-acquired infective diarrhea. Current methods for diagnosing CDI have limitations; enzyme immunoassays for toxin have low sensitivity andClostridioides difficilePCR cannot differentiate infection from colonization. An ideal diagnostic test that incorporates microbial factors, host factors, and host-microbe interaction might characterize true infection. Assessing volatile organic compounds (VOCs) in exhaled breath may be a useful test for identifying CDI. To identify a wide selection of VOCs in exhaled breath, we used thermal desorption-gas chromatography-mass spectrometry to study breath samples from 17 patients with CDI. Age- and sex-matched patients with diarrhea and negative C.difficile testing (no CDI) were used as controls. Of the 65 VOCs tested, 9 were used to build a quadratic discriminant model that showed a final cross-validated accuracy of 74%, a sensitivity of 71%, a specificity of 76%, and a receiver operating characteristic area under the curve of 0.72. If these findings are proven by larger studies, breath VOC analysis may be a helpful adjunctive diagnostic test for CDI.

Metabolic insights at the finish line: deciphering physiological changes in ultramarathon runners through breath VOC analysis

Exhaustive exercise can induce unique physiological responses in the lungs and other parts of the human body. The volatile organic compounds (VOCs) in exhaled breath are ideal for studying the effects of exhaustive exercise on the lungs due to the proximity of the breath matrix to the respiratory tract. As breath VOCs can originate from the bloodstream, changes in abundance should also indicate broader physiological effects of exhaustive exercise on the body. Currently, there is limited published data on the effects of exhaustive exercise on breath VOCs. Breath has great potential for biomarker analysis as it can be collected non-invasively, and capture real-time metabolic changes to better understand the effects of exhaustive exercise. In this study, we collected breath samples from a small group of elite runners participating in the 2019 Ultra-Trail du Mont Blanc ultra-marathon. The final analysis included matched paired samples collected before and after the race from 24 subjects. All 48 samples were analyzed using the Breath Biopsy Platform with GC-Orbitrap™ via thermal desorption gas chromatography-mass spectrometry. The Wilcoxon signed-rank test was used to determine whether VOC abundances differed between pre- and post-race breath samples (adjustedP-value < .05). We identified a total of 793 VOCs in the breath samples of elite runners. Of these, 63 showed significant differences between pre- and post-race samples after correction for multiple testing (12 decreased, 51 increased). The specific VOCs identified suggest the involvement of fatty acid oxidation, inflammation, and possible altered gut microbiome activity in response to exhaustive exercise. This study demonstrates significant changes in VOC abundance resulting from exhaustive exercise. Further investigation of VOC changes along with other physiological measurements can help improve our understanding of the effect of exhaustive exercise on the body and subsequent differences in VOCs in exhaled breath.

Exogenous Volatile Organic Compound (EVOC®) Breath Testing Maximizes Classification Performance for Subjects with Cirrhosis and Reveals Signs of Portal Hypertension

Background: Cirrhosis detection in primary care relies on low-performing biomarkers. Consequently, up to 75% of subjects with cirrhosis receive their first diagnosis with decompensation when causal treatments are less effective at preserving liver function. We investigated an unprecedented approach to cirrhosis detection based on dynamic breath testing. Methods: We enrolled 29 subjects with cirrhosis (Child-Pugh A and B), and 29 controls. All subjects fasted overnight. Breath samples were taken using Breath Biopsy® before and at different time points after the administration of 100 mg limonene. Absolute limonene breath levels were measured using gas chromatography-mass spectrometry. Results: All subjects showed a >100-fold limonene spike in breath after administration compared to baseline. Limonene breath kinetics showed first-order decay in >90% of the participants, with higher bioavailability in the cirrhosis group. At the Youden index, baseline limonene levels showed classification performance with an area under the roc curve (AUROC) of 0.83 ± 0.012, sensitivity of 0.66 ± 0.09, and specificity of 0.83 ± 0.07. The best performing timepoint post-administration was 60 min, with an AUROC of 0.91, sensitivity of 0.83 ± 0.07, and specificity of 0.9 ± 0.06. In the cirrhosis group, limonene bioavailability showed a correlation with MELD and fibrosis indicators, and was associated with signs of portal hypertension. Conclusions: Dynamic limonene breath testing enhances diagnostic performance for cirrhosis compared to static testing. The correlation with disease severity suggests potential for monitoring therapeutic interventions. Given the non-invasive nature of breath collection, a dynamic limonene breath test could be implemented in primary care.

Breath Biopsy® to Identify Exhaled Volatile Organic Compounds Biomarkers for Liver Cirrhosis Detection

Background and Aims

The prevalence of chronic liver disease in adults exceeds 30% in some countries and there is significant interest in developing tests and treatments to help control disease progression and reduce healthcare burden. Breath is a rich sampling matrix that offers non-invasive solutions suitable for early-stage detection and disease monitoring. Having previously investigated targeted analysis of a single biomarker, here we investigated a multiparametric approach to breath testing that would provide more robust and reliable results for clinical use.

Methods

To identify candidate biomarkers we compared 46 breath samples from cirrhosis patients and 42 from controls. Collection and analysis used Breath Biopsy OMNI™, maximizing signal and contrast to background to provide high confidence biomarker detection based upon gas chromatography mass spectrometry (GC-MS). Blank samples were also analyzed to provide detailed information on background volatile organic compounds (VOCs) levels.

Results

A set of 29 breath VOCs differed significantly between cirrhosis and controls. A classification model based on these VOCs had an area under the curve (AUC) of 0.95±0.04 in cross-validated test sets. The seven best performing VOCs were sufficient to maximize classification performance. A subset of 11 VOCs was correlated with blood metrics of liver function (bilirubin, albumin, prothrombin time) and separated patients by cirrhosis severity using principal component analysis.

Conclusions

A set of seven VOCs consisting of previously reported and novel candidates show promise as a panel for liver disease detection and monitoring, showing correlation to disease severity and serum biomarkers at late stage.

Abstract 3319: Breath-based detection of lung cancer using exogenous volatile organic compound targeting β-glucuronidase in the tumor microenvironment

Introduction: Numerous studies have sought potential breath biomarkers for lung cancer and many have promising results but, to date, no validated biomarkers with clear connections to cancer metabolism have been discovered. We aim to show the feasibility of an Exogenous Volatile Organic Compounds (EVOC®) Probe targeting tumor-associated extracellular β-glucuronidase, a glycosidase enzyme that usually resides intracellularly within lysosomes in healthy tissues.

Material and Methods: To further assess the suitability of β-glucuronidase as a target for a non-invasive breath test, the enzyme activity was evaluated by enzymatic assay in lung cancer PDX specimens and healthy tissues. In addition, β-glucuronidase was assessed by immunostaining a large panel of primary lung cancers, lymph node metastasis and normal lung tissue, including from smokers and those with chronic obstructive pulmonary disease (COPD). We developed a hydrophilic non-cell permeable substrate probe, D5-ethyl-βD-glucuronide (D5-EtGlu), that upon hydrolysis by the target enzyme releases D5-ethanol, a unique volatile reporter molecule. This provides a readout of tumour-associated enzyme activity using breath analysis. Administering D5-EtGlu to mice resulted in tumour-specific release of D5-Ethanol enabling discrimination between healthy and tumour-bearing animals. D5-EtGlu has been administered intravenously to healthy and lung cancer patients followed by breath analysis. A phase 1a clinical trial administered D5-EtGlu to 21 healthy individuals in a single ascending dose study to establish safety and background D5-ethanol levels in healthy individuals. The phase 1b trial is a proof of mechanism study in humans, in which D5-ethanol breath levels in lung cancer patients will be compared to cancer-free individuals receiving the same D5-EtGlu dose.

Results and Discussions: Using ex-vivo specimens, higher β-glucuronidase activity was detected in washouts of PDX specimens compared with healthy tissue samples from mice. Higher β-glucuronidase intracellular and extracellular expression was observed in lung cancers compared with lung normal tissue, with low to moderate expression intracellularly in bronchial tissue and in emphysema and COPD. These results reinforce the presence of β-glucuronidase in the tumour microenvironment and its suitability as a target for a breath-probe. A phase 1a resulted in no adverse events and low/no D5-ethanol signal verifying the inaccessibility of D5-EtGlu to intracellular β-glucuronidase. In the phase 1b study, using the highest probe dose, we have detected a D5-ethanol signal in the majority of the cancer patients.

Conclusion: β-glucuronidase can be targeted by the non-cell permeable substrate probe D5-ethyl-βD-glucuronide (D5-EtGlu) with potential to be used as a non-invasive breath test for lung cancer diagnosis including a role in screening.

Citation Format: Christiaan Labuschagne, Rob Smith, Neelam Kumar, Max Allsworth, Billy Boyle, Sam Janes, Philip Crosbie, Robert Rintoul. Breath-based detection of lung cancer using exogenous volatile organic compound targeting β-glucuronidase in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3319.

Breath biopsy early detection of lung cancer using an EVOC probe targeting tumor-specific extracellular β-glucuronidase

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Background: Lung cancer is a leading cause of mortality with 5-year survival less than 20%, largely a result of many cases being diagnosed late. Early detection can increase cancer survival up to 13-fold underscoring the need for effective screening. Targeted Low dose computed tomography (LDCT) has been shown to be effective but its impact to date has been limited due to slow adoption and variable uptake in high-risk populations. Breath analysis represents a non-invasive screening approach either alone or alongside LDCT. Numerous studies have investigated potential endogenous breath biomarkers of lung cancer. Many have produced promising results but to date, no validated biomarkers with clear connections to cancer metabolism have been revealed. We have explored an alternative, probe-based approach based around Exogenous Volatile Organic Compound Probes (EVOC Probes). The probes target tumour associated extracellular b-glucuronidase, a glycosidase enzyme that normally resides within lysosomes. Methods: We use a hydrophilic non cell permeable substrate probe D5-ethyl-βD-glucuronide (D5-EtGlu) that upon hydrolysis by the target enzyme releases D5-ethanol, a unique volatile reporter molecule detectable on breath. This provides a readout of tumour associated enzyme activity using breath analysis. Results: Administering D5-EtGlu to mice resulted in tumour specific release of D5-ethanol, enabling discrimination between healthy and tumour bearing animals. Increased expression of b-glucuronidase in lung cancer tissue and the tumour microenvironment was confirmed with immunohistochemistry (IHC) in clinical samples. A phase 1a clinical trial administered D5-EtGlu to healthy individuals in a single ascending dose study to establish safety and background D5-ethanol levels in healthy individuals. This resulted in no adverse events and low/no D5-ethanol signal verifying the inaccessibility of D5-EtGlu to intracellular b-glucuronidase. The next stage, currently ongoing, is a proof of mechanism in humans. D5-EtGlu is administered intravenously to confirmed lung cancer patients followed by breath analysis. D5-ethanol breath levels will be compared to cancer free individuals receiving the same dose of D5-EtGlu. Conclusions: Non-invasive breath testing has great potential to contribute to diagnosis for lung cancer including a potential role in screening. Our current work is evaluating the use of an administered probe to stimulate tumour-specific enzyme activity and produce a marker detectable on breath. Continued success could result in a sensitive and highly specific method for lung cancer early detection.

The SARS-CoV-2 viral load in COVID-19 patients is lower on face mask filters than on nasopharyngeal swabs

Face masks and personal respirators are used to curb the transmission of SARS-CoV-2 in respiratory droplets; filters embedded in some personal protective equipment could be used as a non-invasive sample source for applications, including at-home testing, but information is needed about whether filters are suited to capture viral particles for SARS-CoV-2 detection. In this study, we generated inactivated virus-laden aerosols of 0.3–2 microns in diameter (0.9 µm mean diameter by mass) and dispersed the aerosolized viral particles onto electrostatic face mask filters. The limit of detection for inactivated coronaviruses SARS-CoV-2 and HCoV-NL63 extracted from filters was between 10 to 100 copies/filter for both viruses. Testing for SARS-CoV-2, using face mask filters and nasopharyngeal swabs collected from hospitalized COVID-19-patients, showed that filter samples offered reduced sensitivity (8.5% compared to nasopharyngeal swabs). The low concordance of SARS-CoV-2 detection between filters and nasopharyngeal swabs indicated that number of viral particles collected on the face mask filter was below the limit of detection for all patients but those with the highest viral loads. This indicated face masks are unsuitable to replace diagnostic nasopharyngeal swabs in COVID-19 diagnosis. The ability to detect nucleic acids on face mask filters may, however, find other uses worth future investigation.

Breath Biopsy Assessment of Liver Disease Using an Exogenous Volatile Organic Compound-Toward Improved Detection of Liver Impairment

INTRODUCTION

Liver cirrhosis and its complication - hepatocellular carcinoma (HCC) - have been associated with increased exhaled limonene. It is currently unclear whether this increase is more strongly associated with the presence of HCC or with the severity of liver dysfunction.

METHODS

We compared the exhaled breath of 40 controls, 32 cirrhotic patients, and 12 cirrhotic patients with HCC using the Breath Biopsy platform. Breath samples were analyzed by thermal desorption-gas chromatography-mass spectrometry. Limonene levels were compared between the groups and correlated to bilirubin, albumin, prothrombin time international normalized ratio, and alanine aminotransferase.

RESULTS

Breath limonene concentration was significantly elevated in subjects with cirrhosis-induced HCC (M: 82.1 ng/L, interquartile range [IQR]: 16.33-199.32 ng/L) and cirrhosis (M: 32.6 ng/L, IQR: 6.55-123.07 ng/L) compared with controls (M: 6.2 ng/L, IQR: 2.62-9.57 ng/L) (P value = 0.0005 and 0.0001, respectively) with no significant difference between 2 diseased groups (P value = 0.37). Levels of exhaled limonene correlated with serum bilirubin (R = 0.25, P value = 0.0016, r = 0.51), albumin (R = 0.58, P value = 5.3e-8, r = -0.76), and international normalized ratio (R = 0.29, P value = 0.0003, r = 0.51), but not with alanine aminotransferase (R = 0.01, P value = 0.36, r = 0.19).

DISCUSSION

Exhaled limonene levels are primarily affected by the presence of cirrhosis through reduced liver functional capacity, as indicated by limonene correlation with blood metrics of impaired hepatic clearance and protein synthesis capacity, without further alterations observed in subjects with HCC. This suggests that exhaled limonene is a potential non-invasive marker of liver metabolic capacity (see Visual abstract, Supplementary Digital Content 1, http://links.lww.com/CTG/A388).