Hello @nr111, Welcome to Connect, an online community where patients and caregivers share their experiences, find support and exchange information with others. I found some information that I think may answer some of your questions.

"A positive PEth result means that the donor has consumed ethanol sometime during the last 2-4 weeks (approximately). Is testing PEth in dried blood spot and ..." --- PEth FAQ’s for Research Only Specimens: PEth FAQ’s for Research Only Specimens

@toolsd has posted in the following discussion and may have some suggestions or answers for your question -- Other causes of failed PEth test for alcohol abuse?: https://connect.mayoclinic.org/discussion/can-failed-peth-test-for-alchohol-abuse-be-caused-by-physical-conditio/

Did you recently have a PETH test in the hospital?