Understanding False Positive ETG Test Results

Introduction

ETG (Ethyl Glucuronide) testing has become a trusted method for detecting alcohol use in probation, workplace monitoring, and rehabilitation programs. Because it can identify even trace amounts of alcohol consumed up to 80 hours prior, many consider it a dependable measure of sobriety.
However, ETG’s high sensitivity is also its greatest weakness. In some cases, people who have not consumed alcohol at all receive a false positive ETG result a finding that can have serious legal, professional, and personal consequences.
Understanding what causes false positives and how to address them is essential for anyone subject to alcohol monitoring.

What Is a False Positive ETG Test?

A false positive occurs when the ETG test detects alcohol metabolites in the body even though the person has not intentionally consumed alcoholic beverages.

ETG forms whenever the body processes ethanol, a chemical found not only in alcoholic drinks but also in many common products such as:

• Mouthwash and breath sprays
• Hand sanitizers
• Perfumes, lotions, and aftershaves
• Cleaning products and solvents
• Certain medications and herbal tinctures

Because ETG testing identifies the presence of ethanol’s byproducts, any exposure to alcohol-based substances can produce detectable ETG levels, especially in very sensitive tests with low cutoff thresholds.

Why False Positives Matter

False positive ETG results can lead to:

• Probation or parole violations
• Loss of custody in family court cases
• Employment termination in safety-sensitive industries
• Emotional distress and damage to reputation

For individuals in recovery or under court supervision, a false result can undermine trust and lead to penalties that are unjustified. Therefore, both test subjects and administrators must understand the limitations and context of ETG testing.

How ETG Testing Works and Why It’s Sensitive

ETG is created when the liver combines ethanol with glucuronic acid. Unlike breath or blood tests, ETG testing doesn’t detect the presence of alcohol itself but rather this metabolite that remains after alcohol has been broken down.

Because ETG can persist in urine for up to 3–4 days, even small, non-beverage exposures can register as positive. Laboratories use cutoff levels typically 100, 500, or 1000 nanograms per milliliter (ng/mL) to decide what counts as a positive result.

• 100 ng/mL: extremely sensitive; detects incidental exposure
• 500 ng/mL: balances sensitivity and specificity (widely used)
• 1000 ng/mL: focuses on intentional drinking

When labs or agencies choose very low cutoffs, the chance of false positives increases significantly.

Common Causes of False Positive ETG Results

1. Personal Hygiene Products

Alcohol-based hand sanitizers, perfumes, deodorants, and aftershaves contain high concentrations of ethanol. Frequent or prolonged use can allow trace absorption through the skin or inhalation, especially in poorly ventilated environments.

2. Mouthwash and Breath Sprays

Many over-the-counter mouthwashes contain 15–25% alcohol. Rinsing multiple times a day can cause enough exposure to register in a sensitive ETG test.

3. Medications and Health Products

Liquid cold syrups, cough medicines, and herbal tinctures often contain ethanol as a solvent. Even small doses may affect ETG levels within a few hours of ingestion.

4. Foods and Fermented Products

Certain foods naturally contain or produce ethanol during fermentation such as ripe fruits, vinegar, soy sauce, kombucha, and energy drinks. Though usually minimal, repeated consumption can influence low-threshold tests.

5. Occupational or Environmental Exposure

Working in environments where alcohol vapors are present (bars, hospitals, cleaning services, beauty salons) may lead to mild inhalation exposure that could appear as a positive result in extremely sensitive testing.

6. Medical or Metabolic Factors

Rarely, specific medical conditions like diabetes or gastrointestinal fermentation syndrome can produce endogenous ethanol, leading to low-level ETG presence even in the absence of alcohol use.

Distinguishing True Positives from False Positives

Professionally administered ETG testing programs use several safeguards to differentiate genuine drinking from incidental exposure:

1. Appropriate Cutoff Levels:
   Laboratories typically use 500–1000 ng/mL to minimize false results.
2. Confirmatory Testing:
   If an initial screen is positive, GC-MS or LC-MS/MS confirmation helps rule out laboratory errors.
3. Clinical Review:
   Counselors or probation officers review behavior, history, and other evidence before concluding that drinking occurred.
4. Documentation of Exposure:
   Maintaining a list of products used before testing can help demonstrate non-intentional contact.

What To Do If You Receive a False Positive ETG Result

1. Request a Retest or Confirmation

If you believe the result is inaccurate, request that the original sample be retested using a confirmatory analytical method. Labs typically store samples for a limited period after initial testing.

2. Gather Evidence

Provide receipts, product labels, or prescriptions showing exposure to alcohol-containing items around the testing period. This documentation helps establish context for your defense.

3. Inform Your Supervisor or Legal Representative

Immediately notify your probation officer, attorney, or program coordinator. Prompt communication demonstrates transparency and responsibility.

4. Seek Expert Evaluation

A medical review officer (MRO) or toxicologist can interpret the test data scientifically, considering potential sources of incidental exposure.

5. Avoid Future Exposure

After a false positive, switch to alcohol-free personal care products and check medication labels carefully. Many brands now market “alcohol-free” alternatives specifically for individuals in recovery or under supervision.

Improving the Accuracy of ETG Testing Programs

To reduce the likelihood of false positives, organizations should:

• Use validated laboratories with established quality controls
• Maintain chain-of-custody documentation for all samples
• Set reasonable cutoff limits aligned with SAMHSA or court guidelines
• Provide educational materials to clients about alcohol-containing products
• Encourage transparency rather than punishment for honest mistakes

By following these practices, agencies can ensure that ETG testing remains both scientifically valid and ethically fair.

Legal and Ethical Considerations

Courts have increasingly recognized that ETG tests, while valuable, must be interpreted with caution. Over-reliance on a single positive result especially at low levels can violate principles of fairness and due process.

Legal professionals often argue for:

• Independent confirmation before sanctions
• Disclosure of laboratory cutoff levels
• Expert testimony explaining ETG’s limitations

For individuals under legal supervision, knowing their rights and maintaining documentation of daily activities can make a significant difference in contesting questionable results.

Conclusion

ETG testing is a powerful tool for monitoring alcohol use, but like all biochemical tests, it is not infallible. False positives can occur from everyday products, medical conditions, or environmental factors.

Understanding these risks and taking proactive steps such as avoiding alcohol-based items, requesting confirmatory testing, and maintaining honest communication with authorities — can help protect individuals from unfair penalties.

Ultimately, responsible use of ETG testing requires scientific precision, legal fairness, and human understanding.