Molecular breath analysis supports altered amino acid metabolism in idiopathic pulmonary fibrosis.

BACKGROUND AND OBJECTIVE: Diagnosis of idiopathic pulmonary fibrosis (IPF) is complex and its pathogenesis is poorly understood. Recent findings indicate elevated levels of proline and other amino acids in lung tissue of IPF patients which may also be of diagnostic value. Following these findings, we hypothesized that such altered metabolic profiles would be mirrored in exhaled breath and could therefore be captured non-invasively in real time. METHODS: We aimed to validate these results using real-time exhaled breath analysis by secondary electrospray ionization-mass spectrometry, which can provide a non-invasive, painless and fast insight into the metabolism. Breath analysis was performed in a matched 1:1 case-control study involving 21 patients with IPF and 21 control subjects. RESULTS: We found significantly (P < 0.05) elevated levels of proline, 4-hydroxyproline, alanine, valine, leucine/isoleucine and allysine in breath of IPF patients, whereas pyroglutamic acid and phenylalanine did not show significant differences. This coincides with the amino acid's abundance in pulmonary tissue indicating that our observations reflect progressing fibrosis. In addition, amino acid levels correlated across subjects, further supporting a common underlying pathway. We were able to obtain a cross-validated area under the curve of 0.86, suggesting that these increased amino acid levels in exhaled breath have the potential to be used as biomarkers for IPF. CONCLUSION: We could validate previous findings of elevated lung tissue amino acid levels in IPF and show that online breath analysis might be a practical tool for a rapid screening for IPF.

Real-Time Breath Analysis Reveals Specific Metabolic Signatures of COPD Exacerbations.

BACKGROUND: Exacerbations of COPD are defined by acute worsening of respiratory symptoms leading to a change in therapy. Identifying altered metabolic processes in patients at risk for future exacerbations is desirable for treatment optimization, the development of new therapeutic strategies, and perhaps diagnostic value. We aimed to identify affected pathways using the profiles of volatile organic compounds in exhaled breath from patients with COPD with and without frequent exacerbations (≥ 2 exacerbations within the past 12 months). METHODS: In this matched cohort study, exhaled breath profiles from patients with COPD and frequent exacerbations ("frequent exacerbators") and without frequent exacerbations ("nonfrequent exacerbators") were analyzed during an exacerbation-free interval using real-time secondary electrospray ionization high-resolution mass spectrometry. We analyzed exhaled breath from 26 frequent exacerbators and 26 nonfrequent exacerbators that were matched in terms of age, sex, and smoking history. To obtain new pathophysiological insights, we investigated significantly altered metabolites, which can be assigned to specific pathways. Metabolites were identified by using a Wilcoxon rank-sum test. RESULTS: Metabolite levels from the ω-oxidation pathway, namely ω-hydroxy, ω-oxo, and dicarboxylic acids, were consistently decreased in frequent exacerbators. Additionally, several new nitro-aromatic metabolites, which were significantly increased in frequent exacerbators, were identified. CONCLUSIONS: Real-time breath analysis by secondary electrospray high-resolution mass spectrometry allows molecular profiling of exhaled breath, providing insights about ongoing biochemical processes in patients with COPD at risk for exacerbations. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT02186639; URL: www.clinicaltrials.gov.

Real-time exhaled breath analysis in patients with cystic fibrosis and controls.

We aimed at defining profiles of volatile organic compounds in exhaled breath from patients with cystic fibrosis (CF) using a novel real-time mass spectrometry technique. In this prospective matched case-control study, 30 patients with CF, and 30 healthy control subjects were matched one-to-one according to age, gender, and smoking state. We performed exhaled breath analysis by untargeted secondary electrospray ionization-high resolution mass spectrometry (SESI-HRMS). Patients with CF (mean age 26.0 ± 13.0 years) and controls (mean age 27.9 ± 14.0 years) were analyzed using SESI-HRMS. 49 exhaled breath features were found to be altered (p-value < 0.05/q-value < 0.1) in CF patients, in comparison to healthy controls. The two most discriminating features showed a prediction AUROC of 77.1% (95% CI 62.2%-87.8%) with a specificity of 80.0% and a sensitivity of 63.3%. Levels of oxidative stress metabolites such as fatty acids were found to differ significantly between patients with CF and healthy controls. Furthermore, in patients with CF, 11 features correlated with the mucus concentration of Stenotrophomonas maltophilia bacteria. Exhaled breath analysis with SESI-HRMS allows the identification of CF specific compounds in real-time and may trace bacterial strains in affected patients with CF.

Real-time mass spectrometric identification of metabolites characteristic of chronic obstructive pulmonary disease in exhaled breath.

Background: New mass spectrometry (MS) techniques analysing exhaled breath have the potential to better define airway diseases. Here, we present our work to profile the volatile organic compounds (VOCs) in exhaled breath from patients with chronic obstructive pulmonary disease (COPD), using real-time MS, and relate this disease-specific breath profile to functional disease markers. Methods: In a matched cohort study, patients with COPD, according to GOLD criteria, were recruited. Exhaled breath analysis by untargeted MS was performed using secondary electrospray ionization - high-resolution MS (SESI-HRMS). Results: Exhaled breath from 22 patients with COPD (mean age 58.6 ±â€¯6.9 years, FEV1 58.5 ±â€¯19.9% predicted, 32.4 ±â€¯19.2 pack years smoking) and 14 controls (mean age 58.1 ±â€¯8.1 years, FEV1 102.5 ±â€¯11.3% predicted, 23.6 ±â€¯12.5 pack years smoking) was analysed using SESI-HRMS. From 1441 different features, 43 markers were identified that allowed discrimination between the two groups with an accuracy of 89% (CI 74-97%), a sensitivity of 93%, and a specificity of 86%. The markers were determined to be metabolites of oxidative stress processes, such as fatty acids, aldehydes and amino acids, resulting from lung muscle degradation. Conclusion: Real-time breath analysis by SESI-MS allows molecular profiling of exhaled breath, can distinguish patients with COPD from matched healthy controls and provides insights into the disease pathogenesis.