From the Guidelines
Phosphatidylethanol (PEth) testing is a highly sensitive and specific blood test for detecting alcohol consumption over the past 2-4 weeks, with a sensitivity of 100% and specificity of 96% for a cutoff of over 20 ng/mL, as reported by CRaBB et al. in Hepatology, Vol. 71, No. 1,2020 1. Phosphatidylethanol (PEth) testing works by measuring phosphatidylethanol, a direct biomarker that forms in red blood cells only when alcohol is consumed. Key characteristics of PEth testing include:
- A half-life of approximately 10-14 days, which can be longer with more chronic, repeated heavy alcohol consumption 1
- Not influenced by age, body mass index (BMI), sex, kidney disease, or liver disease, although women may have higher PEth levels for a given amount of alcohol consumption compared with men 1
- Inter-individual variations in PEth metabolism, but validated in a study of chronic liver disease patients at a cutoff of 80 ng/mL for four drinks per day or more with a sensitivity of 91% and specificity of 77% 1 The test requires a blood sample, typically collected via fingerstick or venipuncture, and results are usually reported in nanograms per milliliter (ng/mL). PEth testing is considered more reliable than self-reported alcohol use and other biomarkers, as it is less affected by other medical conditions or medications, making it particularly useful for monitoring abstinence in treatment programs, legal cases involving alcohol use, or in liver transplant candidates 1.
From the Research
Phosphatidylethanol Testing
Phosphatidylethanol (PEth) testing is a method used to identify hazardous alcohol use. The test measures the level of PEth in the blood, which is a molecule formed from phosphatidylcholine and ethanol through transphosphatidylation catalyzed by phospholipase D 2.
How PEth Testing Works
- PEth formation requires ethanol and accumulates in the blood upon repeated ethanol exposure 2.
- The level of PEth in the blood correlates with alcohol intake at the population level, although there is considerable inter-individual variation 2.
- The test is used to identify patients with problematic alcohol use who may be missed by other screening methods, such as the Alcohol Use Disorders Identification Test (AUDIT) questionnaire 3.
Interpretation of PEth Test Results
- PEth values below the lower reporting limit (typically ∼0.03-0.05 µmol/L, or ∼20-35 µg/L) indicate sobriety or only low or occasional alcohol consumption 2.
- Regular high alcohol intake at levels corresponding to harmful drinking is required in most cases to reach PEth values > 0.30 µmol/L 2.
- The correlation between PEth values and AUDIT scores is moderate, with some patients having high PEth values despite low AUDIT scores 3.
Clinical Applications of PEth Testing
- PEth testing can be used as an additional screening method for hazardous alcohol use in the Emergency Department 3.
- The test can also be used in primary health care to identify patients with hazardous alcohol use and to monitor treatment follow-up 4.
- PEth testing has been shown to improve the prerequisites for the GP-patient interaction, although it can also make the interaction more complex 4.
Limitations and Future Directions
- Further research is needed to elucidate the variability in PEth formation and degradation, as well as the molecular mechanisms behind that variability 5.
- The use of PEth testing in clinical practice is still evolving, and more studies are needed to determine its role in the diagnosis and treatment of alcohol use disorder 6.