Non-13CO2 targeted breath tests: a feasibility study

Breath tests allow a non-invasive and fast diagnostic of different specific enzymes’ phenotypic functionality. Over the last decade several 13C-breath tests were successfully tested, with the 13C-urea breath test being approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). The use of other targets than labeled 13CO2 in exhaled breath offers additional possibilities. High sensitivity analytical technologies, such as proton-transfer reaction time-of-flight mass spectrometry, enable the detection of different volatile targets in the low ppb (parts per billion) range in real-time.In the current study volunteers received 0.8 mg deuterated 2-propanol, which was converted to d3-acetone (m/z 62.08) by alcohol dehydrogenase. D3-acetone (m/z 62.08) appeared in exhaled breath concentrations up to 30 ppb (at maximum). Parallel consumption of ethanol seems to reduce the activity of the enzyme, resulting in approximately 15–30% reduction of the produced d3-acetone. Phenotypic determination of enzyme activities is important, since the functionality of enzymes is influenced by factors such as age, sex, life-style, diet, organ function, metabolism, etc, which cannot be entirely accounted for by genetic factors.