Distinguish oral-source VOCs and control their potential impact on breath biomarkers

By means of glass bottle sampling followed by solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS) technique, the change characteristics of volatile organic compounds (VOCs) in breaths, between before gargling and after gargling, were investigated, respectively, in 41 healthy subjects and 50 esophageal cancer patients. Using an untargeted strategy, 143 VOC chromatographic peaks were enrolled in the statistical analysis. Based on the orthogonal partial least squares discriminant analysis (OPLS-DA), the VOC variations after gargling for each breath test group were obtained according to the combined criteria of variable importance in projection (VIP > 1.5), Wilcoxon signed-rank test (P < 0.05), and fold change (FC > 2.0). When gargled, the levels of indole, phenol, 1-propanol, and p-cresol in the breath of healthy people decreased; meanwhile, for esophageal cancer patients, the declined VOCs in breath were indole, phenol, dimethyl disulfide, and p-cresol. Particularly, these substances were previously reported as breath biomarkers in some diseases such as esophageal, gastric, thyroid, breast, oral, and lung cancers, as well as certain non-cancer disorders. The present work indicates that expiratory VOCs involve the prominent oral cavity source, and in the breath biomarkers study, the potential impact that originates from oral volatiles should be considered. In view of the present results, it is also proposed that gargle pretreatment could eliminate possible interference from the oral cavity VOCs that might benefit breath biomarker investigation.

Automated summary

This study investigated the change characteristics of volatile organic compounds (VOCs) in breaths before and after gargling in healthy subjects and esophageal cancer patients using glass bottle sampling and solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS) technique. The results showed that the levels of certain VOCs decreased after gargling in both healthy individuals and esophageal cancer patients. These substances have been previously reported as breath biomarkers in various diseases. The study suggests that expiratory VOCs from the oral cavity should be considered in breath biomarker research, and gargle pretreatment could eliminate interference from oral cavity VOCs, benefiting breath biomarker investigation.