From the Guidelines
To confirm if a patient has been drinking alcohol, the most reliable lab test is a combination of carbohydrate-deficient transferrin (CDT) and gamma-glutamyl transferase (GGT), which can detect recent and chronic alcohol consumption, as supported by the most recent study from 2020 1. When considering the detection of alcohol consumption, it's essential to understand the different timeframes and sensitivities of various lab tests.
- For recent alcohol consumption, tests such as blood alcohol concentration (BAC) can detect ethanol levels in the bloodstream within the past 12-24 hours.
- For longer-term monitoring, CDT and GGT are useful as they remain elevated for 2-4 weeks after heavy drinking, with CDT having a sensitivity of 25%-50% and GGT having a sensitivity of 42-86% 1.
- Other tests like ethyl glucuronide (EtG) and ethyl sulfate (EtS) urine tests can detect alcohol use for up to 80 hours after consumption, with EtG having a sensitivity of 89% and specificity of 99% 1.
- Phosphatidylethanol (PEth) blood testing offers an even longer detection window of 2-4 weeks and is highly specific for alcohol.
- Mean corpuscular volume (MCV) and liver function tests like AST and ALT can indicate chronic alcohol use but are less specific, with MCV having a sensitivity of 24-75% and AST having a sensitivity of 43-68% 1. It's crucial to consider the timeframe being investigated and to understand that some tests like GGT can be elevated due to other conditions or medications, as noted in the 2018 study 1.
- A combination of tests often provides the most accurate assessment of a patient's alcohol consumption patterns, as each test has its limitations and confounding factors, such as liver disease, BMI, sex, and drugs 1.
- The 2020 study from the American Association for the Study of Liver Diseases emphasizes the importance of discussing biomarker use with patients before testing to maintain therapeutic alliance and improve alcohol use disclosure 1.
From the Research
Lab Tests to Confirm Alcohol Consumption
To confirm if a patient is drinking alcohol, several lab tests can be used, including:
- Carbohydrate-deficient transferrin (CDT) 2, 3, 4, 5, 6
- Gamma-glutamyl transferase (GGT) 2, 3, 4, 5, 6
- Mean corpuscular volume (MCV) 2, 5
- Phosphatidyl ethanol (PEth) 5
- Fatty acid ethyl ester (FAEE) 5
- Total serum sialic acid (TSA) 5
- Alanine aminotransferase (ALT) 5
- Aspartate aminotransferase (AST) 5
- Cholesteryl ester transfer protein (CETP) 5
Characteristics of Lab Tests
The characteristics of these lab tests vary, including:
- Sensitivity: CDT has a sensitivity of 67% 2, while GGT has a sensitivity of 42% 2
- Specificity: CDT has a specificity of 97% 2, while GGT has a specificity of 76% 2
- Time period for detection: The time period for detection of alcohol use varies among the lab tests, with some detecting recent use and others detecting longer-term use 5
Clinical Implications
The clinical implications of these lab tests include:
- Detection of high-risk drinking: CDT and other lab tests can be used to detect high-risk drinking in patients 6
- Monitoring treatment outcome: Consecutive measurements of CDT and GGT can be used to monitor treatment outcome in patients with alcohol dependence 4
- Identification of individual baseline values: CDT and GGT measurements can be used to identify individual baseline values for patients, which can be useful in monitoring treatment outcome 4