Cut-Point Levels of Phosphatidylethanol to Identify Alcohol Misuse in a Mixed Cohort Including Critically Ill Patients

Background: Although alcohol misuse is associated with deleterious outcomes in critically ill patients, its detection by either self-report or examination of biomarkers is difficult to obtain consistently. Phosphatidylethanol (PEth) is a direct alcohol biomarker that can characterize alcohol consumption patterns; however, its diagnostic accuracy in identifying misuse in critically ill patients is unknown.

Methods: PEth values were obtained in a mixed cohort comprising 122 individuals from medical and burn intensive care units (n = 33), alcohol detoxification unit (n = 51), and healthy volunteers (n = 38). Any alcohol misuse and severe misuse were referenced by Alcohol Use Disorders Identification Test (AUDIT) and AUDIT-C scores separately. Mixed-effects logistic regression analysis was performed, and the discrimination of PEth was evaluated using the area under the receiver-operating characteristic (ROC) curve.

Results: The area under the ROC curve for PEth was 0.927 (95% CI: 0.877, 0.977) for any misuse and 0.906 (95% CI: 0.850, 0.962) for severe misuse defined by AUDIT. By AUDIT-C, the area under the ROC curves was 0.948 (95% CI: 0.910, 0.956) for any misuse and 0.913 (95% CI: 0.856, 0.971) for severe misuse. The PEth cut-points of ≥250 and ≥400 ng/ml provided optimal discrimination for any misuse and severe misuse, respectively. The positive predictive value for ≥250 ng/ml was 88.7% (95% CI: 77.5, 95.0), and the negative predictive value was 86.7% (95% CI: 74.9, 93.7). PEth ≥ 400 ng/ml achieved similar values, and similar results were shown for AUDIT-C. In a subgroup analysis of critically ill patients only, test characteristics were similar to the mixed cohort.

Conclusions: PEth is a strong predictor and has good discrimination for any and severe alcohol misuse in a mixed cohort that includes critically ill patients. Cut-points at 250 ng/ml for any, and 400 ng/ml for severe, are favorable. External validation will be required to establish these cut-points in critically ill patients.