Phosphatidylethanol (PEth) Homologues Test
Phosphatidylethanol (PEth) homologues test is a highly sensitive and specific biomarker test that detects direct products of ethanol metabolism in blood, capable of detecting a single drinking episode for up to 12 days and chronic heavy alcohol use for up to 6 weeks. 1
What is PEth?
- PEth represents a group of glycerophospholipid homologues formed specifically when ethanol binds to phospholipids through the action of phospholipase D 2
- PEth is a direct biomarker of alcohol consumption with theoretically 100% diagnostic specificity since its formation requires the presence of ethanol 2
- PEth consists of multiple homologues that differ in their fatty acid chain length and degree of unsaturation 3, 4
- The most commonly measured homologue is PEth 16:0/18:1, which is the major homologue in blood samples from alcoholics 3
- Other prevalent homologues include PEth 16:0/18:2,18:0/18:2, and 18:0/18:1 3, 5
Clinical Utility
- PEth testing is now commonly used in the US and Europe to monitor alcohol use in liver transplant centers 1
- PEth levels directly correlate with the amount of alcohol consumed, making it a semi-quantitative measure of alcohol intake 1
- PEth has a half-life of approximately 4 days in blood 2
- PEth is more sensitive than traditional alcohol markers such as CDT (carbohydrate-deficient transferrin), GGT (gamma-glutamyl transferase), and MCV (mean corpuscular volume) 2
Interpretation of Results
- In US commercial labs, 20 ng/ml is the minimum reporting threshold for a positive test 1
- A PEth range of 20–200 ng/ml may indicate alcohol use consistent with MetALD (Metabolic dysfunction and Alcohol-related Liver Disease), which is defined as 20–60 g/day or 140–420 g/week 1
- PEth levels >200 ng/ml (typically >500 ng/ml) are consistent with drinking above the MetALD range (>50 g/day in women and >60 g/day in men) 1
- In Sweden, a PEth level above 0.30 μmol/L (~210 μg/L) is considered a strong indicator of harmful drinking 6
Advantages Over Other Alcohol Biomarkers
- PEth has higher specificity compared to indirect markers like GGT, AST, ALT, and MCV, which can be altered by other conditions such as drug ingestion, liver disease, or muscle disease 1
- Unlike ethanol testing in blood, breath, or urine, PEth has a much longer detection window 1
- PEth is not affected by the presence of compensated or decompensated cirrhosis, unlike some other markers 1
- PEth can detect a single drinking episode for up to 12 days and chronic heavy use for up to 6 weeks 1
Limitations and Considerations
- PEth only correlates with recent alcohol use and does not account for historical alcohol use 1
- PEth testing should be used as an adjunct to alcohol history taking, standardized questionnaires, and collateral information 1
- The applicability of PEth testing may be limited by its cost 1
- Due to interindividual variations in test response and elimination half-life, it is not possible to indicate the exact amount or time of alcohol intake 6
Technical Aspects
- Modern PEth analysis typically uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) for high sensitivity and specificity 4, 5
- Up to 48 different homologues of PEth have been identified in blood using LC-ESI-MS/MS 4
- Dried blood spots can be used for PEth analysis, allowing for easier sample collection and storage 5
PEth homologues testing represents a significant advancement in alcohol biomarker testing, providing clinicians with a reliable tool to detect and monitor alcohol consumption in various clinical settings, particularly in liver disease management and transplantation evaluation 1.