I think these machines will not be able to give 100% accurate result. In studies of this type there will always be errors. But even if this percentage of accuracy is high, then this will benefit humanity.
This device registers a change in the composition of the gas, deviation from the norm. To make a more accurate diagnosis, you will need to consult a doctor. That's what I understood. Of course, no one will give you a 100% guarantee on the correctness of the result.
but at least it is a warning system if you have diabetes or some other kind of desease
maybe this also could be useful with apple watchs healt system monitor together somehow.