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. 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. In this study of a mixed cohort that includes critically ill patients, PEth demonstrated good discrimination for any alcohol misuse. A cut‐point of ≥ 250 ng/mL provided optimal discrimination for any misuse with a positive predictive value at 88.7% and negative predictive value