Good question….as far as I know they can go up really high. One thing you might want to do us get somebody to run an assay on your Phospholipase D activity. That’s the enzyme that makes PEth. Some people have hyperactive Phospholipase D which would theoretically account for high PEth levels.
I think there was a 2019 article in a French pathology journal that purported to find that alcohol-based hand sanitizers can dramatically raise PEth over a short-term period. There might be a posting if that article on this thread?
Good luck. Remember it sometimes takes its sweet time, but the Truth eventually comes out. Whoever developed and marketed that test with so many variables and compromising factors not even known — much less investigated — ought to think about something called ETHICS.