Real-time selected ion flow tube mass spectrometry to assess short- and long-term variability in oral and nasal breath

Background: Breath based non-invasive diagnostics have the potential to provide valuable information about a person's health status.However, it is not yet widely used in clinical practice due to multiple factors causing variability and the lack of standardized procedures.This study focuses on the comparison of oral and nasal breathing and on variability of volatile metabolites over short and long term.Methods: Selected ion flow tube mass spectrometry (SIFT-MS) was used for on-line analysis of selected volatile metabolites in oral and nasal breath of 10 healthy individuals 5 times in one day (short term) and 6 times spread over 3 weeks (long term) resulting in nearly 100 breath samplings.Intraclass correlation coefficients (ICC) were used to assess short and long term biological variability.Additionally, the composition of ambient air was analyzed at different samplings.The selected volatiles common in exhaled breath were propanol, 2,3-butanedione, acetaldehyde, acetone, ammonia, dimethyl sulfide, isoprene, pentane, and propanal.Additionally, environmental compounds benzene and styrene were analyzed as well.Results: Volatile metabolite concentrations in ambient air were not correlated with those in exhaled breath and were significantly lower than in breath samples.All volatiles showed significant correlation between oral and nasal breath.Five were significantly higher in oral breath compared to nasal breath, while for acetone, propanal, dimethyl sulfide and ammonia concentrations were similar in both matrices.Variability depended on the volatile metabolite.Most physiologically relevant volatiles (acetone, isoprene, propanol, acetaldehyde) showed good to very good biological reproducibility (ICC > 0.61) mainly in oral breath and over a short term period of one day.Conclusion: Both breathing routes showed relatively similar patterns, however bigger differences were expected.Therefore, since sampling from the mouth is practically more easy, the latter might be preferred.