The Science and Significance of Hair Strand Testing for 

Alcohol Use

In forensic toxicology, the analysis of alcohol consumption is crucial in various legal and clinical contexts. Forensic Testing Service (FTS) stands at the forefront of this field, offering expert services in hair strand testing to accurately determine patterns of alcohol use over extended periods.

This article explores the benefits, challenges, and methodologies of hair strand and blood testing for alcohol biomarkers, as shared in a recent expert webinar featuring Damian World, Technical Support and Reporting Manager at FTS, and Steve Nurdin, Senior Account Manager.

Understanding Hair Strand Testing

Hair strand testing is a highly specialised form of toxicological analysis that provides a long-term view of alcohol consumption. Unlike blood, saliva or urine tests, which offer snapshots of recent consumption—hours in the case of blood alcohol concentration and days for urine—hair testing can cover periods of up to nine months. This extended window is invaluable for assessing chronic alcohol use, providing evidence that is crucial in both legal and medical settings.

The principle behind hair testing is straightforward. Alcohol biomarkers, such as ethyl glucuronide (EtG), are formed in the body following the consumption of alcohol. These biomarkers are then transported via the bloodstream into the hair follicles, where they become incorporated into the hair shaft.

Over time, this biomarker remains locked within the hair, offering a historical record of alcohol consumption. For example, FTS can conduct alcohol testing over a 6-month period, to demonstrate an individual’s mean alcohol consumption over this period, if dictated by a court order assessment.

Key Biomarkers: Ethyl Glucuronide (EtG)and Phosphatidylethanol (PEth) Testing

FTS focuses on testing two primary biomarkers in alcohol consumption assessments: EtG and PEth. Both of these are direct metabolites of ethanol, the type of alcohol found in alcoholic beverages, and their presence in hair and blood respectively indicates alcohol consumption.

• Ethyl Glucuronide (EtG): This is the primary biomarker tested by FTS. It is also present in urine and is widely used in alcohol assessments when urine testing is required. The key advantage of EtG is its specificity; it is only formed when ethanol is metabolised by the body, making it a reliable indicator of alcohol consumption.
• Phosphatidylethanol (PEth): PEth is another significant biomarker, found in blood samples. Like EtG, it is a direct metabolite of ethanol and is used to confirm alcohol consumption over the 3 to 4 weeks prior to sample collection. PEth is especially useful in cases where the hair has been exposed to external factors, such as dyes or bleaches, that might strip EtG from the hair.

The Process and Challenges of Hair Strand Testing

Hair strand testing involves more than just the detection of biomarkers. The process must account for various external factors that could affect the accuracy of the interpretations provided. One of the main challenges is the potential removal of biomarkers from the hair due to the use of hair treatments like dyes or bleach. These products open the hair follicle to alter pigmentation, which can also remove substances like EtG from the hair. In such cases, FTS always attempts to test an alternative sample to ensure the reliability of the results.

Moreover, the testing process can be further complicated by factors such as pregnancy, which can cause a significant reduction in biomarkers across all biological samples. This occurs because the developing foetus absorbs alcohol and other substances ingested by the parent, making these biomarkers less available in the mother’s bloodstream, and consequently in the hair. While this factor is crucial, standards used by laboratories other than FTS have not yet established specific cut-off levels for pregnant individuals. FTS, on the other hand, compare results to our database of over 4000 alcohol tests, including those from pregnant individuals, to reach an assessment based on the balance of probabilities.

Segmental Analysis and its Forensic Value

A unique advantage of hair strand testing is the ability to segment hair samples into specific periods of interest. Typically, alcohol biomarker testing is segmented into three-month periods, but FTS can also perform monthly alcohol assessments if required. This capability allows for a more detailed analysis of an individual’s alcohol consumption over specific periods of time, which can be particularly valuable in legal cases where precise timelines are essential.

For instance, in situations where an individual has declared low levels of alcohol consumption say, less than five units per week, FTS’s experience suggests that this would not produce detectable levels of EtG in the hair. However, if an individual reports moderate consumption, around 15 to 30 units per week, this could lead to detectable levels of EtG. Although these might fall below the reporting thresholds used by other providers. At FTS, even such low levels are considered valuable and are reported in the context of the individual’s declared consumption.

The Importance of Expert Interpretation

One of the key takeaways should be the importance of expert interpretation in hair strand testing. The results of these tests are not merely black and white; they require careful consideration of all external factors that could influence the levels of biomarkers detected. This includes assessing the individual’s self-declared exposure to factors like hair treatments, pregnancy, and even the use of products containing alcohol, such as hand sanitisers.

FTS prides itself on its thorough forensic investigations, which consider these overlapping factors to form an expert opinion on what the results are likely to represent. This level of expertise is crucial, as providers who apply strict cut-off values without such contextual analysis may miss critical nuances in the data, potentially leading to incorrect conclusions.

Conclusion

Hair strand testing for alcohol use biomarkers is a powerful tool in forensic toxicology, offering a detailed and long-term view of an individual’s alcohol consumption. However, the accuracy and reliability of the results depend heavily on expert interpretation, which accounts for the many variables that can influence the presence of biomarkers in the hair.

At Forensic Testing Service, our commitment to comprehensive analysis and expert reporting ensures that we provide the most accurate and contextually relevant evidence possible. Whether for legal proceedings or clinical assessments, our hair testing for drug and alcohol services are designed to meet the highest standards of forensic science, offering clarity and precision where it matters most.

Published in the following magazines

Liverpool Law from Liverpool Law Society

Newcastle News from Newcastle Law Society

INBrief – The Journal of the Northern Circuit of the Bar