Phosphatidylethanol as an outcome measure in treatment aimed at controlled drinking.

Background: Phosphatidylethanol (PEth) is a specific marker of alcohol intake, used both as a screening method for hazardous use and as an outcome measure in the treatment of alcohol use disorder (AUD). However, what cut-off values to apply for hazardous use in a treatment setting is still unclear. We aimed to investigate the correlation between PEth and self-reported drinking and identify the optimal cut-off for hazardous use, for patients with AUD and a stated goal of controlled drinking.

Methods: We used data from a randomized controlled trial of two different psychological treatments aiming for controlled drinking, conducted within specialized addiction care in Stockholm, Sweden. A total of 181 patients left samples that could be included in the current analysis. Outcomes were measured at five different time points over 2 years of follow-up. PEth 16:0/18:1 values were correlated with subjective reports of recent drinking based on the Timeline Follow-Back Method.

Results: The correlation between PEth and self-reported alcohol intake increased significantly over time, with the weakest correlation found at baseline (Spearman's ρ = 0.42) and the strongest at the 104-week follow-up (ρ = 0.69). When used to indicate hazardous drinking according to Swedish guidelines (≥10 units per week), receiver operating characteristic analysis revealed PEth ≥ 0.22 μmol/l to be the optimal cut-off.

Conclusions: PEth is a useful outcome measure that can be used to validate subjective reports of current drinking. In a treatment setting aimed at controlled drinking, the accuracy of patients' self-report measures seems to improve over time. In this context, a PEth value of ≥0.22 μmol/l is a sensitive and specific indicator of hazardous drinking.