I joined specifically to comment in this group. I have regular and random alcohol use screening from two separate providers. I consistently pass GGT and CDT test but one provider decided to give me a PEth and Ethyl Glucuronide test. I passed the Ethyl Glucuronide test but had a 653 ng/mL PEth result well above the 20 ng/mL cutoff. Slightly worried and working on my rebuttal. Although this provider is not my primary care physician who actually handles and controls my case she can influence him. I just had an appointment with him and he has little concern about my abstinence. However, non-FDA approved testing can derail that apparently according to peoples posts.

I wanted to share this, it came directly from my lab results which I have full access to:
"Comments: Analyzed compound: PEth 16:0/18:1. 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanol. Analysis performed by Liquid Chromatography with Tandem Mass Spectrometry (LC/MS/MS). Detection limit: 20 ng/mL PEth levels in excess of 20 ng/mL are considered evidence of moderate to heavy ethanol consumption. However, the Center for Substance Abuse Treatment (CSAT) advises caution in interpretation and use of biomarkers alone to assess alcohol use. Results should be interpreted in the context of all available clinical and behavioral information. Reference: Substance Abuse and Mental Health Services Administration (2012). \"The Role of Biomarkers in the Treatment of Alcohol Use Disorders\", 2012 Revision. Advisory, Volume 11, Issue 2. This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration."

I hope the comments will help someone else bolster their case as to the lack of validity using PEth as a sole biomarker.