I've recently been required to submit to periodic blood testing, for professional licensing purposes, due to a diagnosis of harmful use of alcohol.

I had a blood draw on 5 Feb, having last consumed alcohol on NY Eve. I had a fair bit over the evening (I was not required to be abstinent at this point), and then completely stopped drinking. Before that, I'd had a fair bit on Christmas Day, but nothing in between.

My blood test came back fine, as I expected. They'd tested for CDT, GGT, AST, ALT and PEth. My question(s) is, having read up on the subject, how could my PEth level be 28 micro grammes/ L, when I hadn't had a drink for 35 days? More curiously, why does the report say abstinence confirmed, when a lot of people seem to be talking of 20 ng/ml (the same as 28 mg/L right?) as a positive result.

a) Surely my PEth level should have been lower/non-existent?
b) Surely the 28 mg/L does not confirm abstinence (although I was)?

My guess would be the you have an allowance for incidental exposure/disease/or contact of alcohol products. It's also possible that your body didn't completely rid itself of all the alcohol and that may be due to a health issue, as well as some product you may use that contains alcohol.

These are questions for the lab/institution that orders the test for specific answers as to their policy, or procedure.

Thanks for the reply. I did think of asking at my last appointment, but as I have been abstinent, and intend to remain so, I didn't want to appear too interested in their procedures, in case the psychiatrist thought I was angling to "game" the system. After all, if I stay abstinent, I'll be fine, right?

Well, yes, but then, whilst I was drinking too much before January, it wasn't in the industrial quantities of some, and had tailed off from mid-December, when my diagnosis was made. I'm still a little bit curious/uncomfortable that my result came back the way it did. I've seen different values for cutoffs in papers on the net, and 20ng/ml does seem very low. It will be interesting to see what the result is after 5 months of abstinence. I don't really buy the hand sanitizer / alcohol in other products argument - there just wouldn't be enough, and I cook almost all my own food. My health is fine too, as indicated by the normal results of the liver function tests that my blood is tested for.