Breath analysis to diagnose and assess systemic sclerosis using thermal desorption and comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry

Background: Systemic sclerosis (SSc) is a chronic and heterogenous auto-immune disease of unknown origin characterized by fibrosis, inflammation, vascular damages, and involvement of internal organs. Interstitial lung disease (ILD) is one of the most common types of pulmonary involvement, responsible for the disease severity, and leading to high morbidity and mortality. One of the challenges in SSc remains the early diagnosis of patients. There is an unmet need for biological markers enabling SSc early diagnosis, prognosis, disease progression monitoring, and improving patients’ classification for more targeted therapies. Method: Volatiles collected in 5L sampling bags were transferred onto thermal desorption tubes and finally released and separated into a comprehensive two-dimensional gas chromatography system coupled to a high-resolution mass spectrometer. First, the exhaled breath of 32 patients and 30 healthy subjects was analyzed. Next, we investigated deeper patient stratification. Two groups were studied: 21 SSc patients and 21 SSc-ILD patients. This study was multicentric involving Maastricht Medical Center and the University Hospital of Liege. Results: In the first phase, we were able to identify 16 compounds discriminating SSC patients from healthy ones. For the second population, a statistical model using PLS-DA was developed and tested. 9 biomarkers were found as determinant in the classification, achieving a 77% sensitivity and a 100% specificity. Currently, a complementary study is being conducted to relate these biomarkers to possible metabolic pathways. Moreover, this statistical model will be tested on an additional cohort of 26 patients. Conclusion: This work represents a major step to demonstrate the potential of exhaled breath analysis to better understand the metabolomic perturbations due to different forms of SSc. Moreover, the multicentric design helped us to evaluate the robustness of our analytical methods, providing valuable information in the development of general guidelines and SOPs for larger exhaled breath studies