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Why not just hair tests
Hair tests, being direct Markers, are mostly specific to excessive alcohol use, particularly EtG and generally provide a good screening tool to identify excessive drinking. However for a variety of reasons it is extremely important not to rely on hair alone, for the following reasons: A blunt instrument - Hair tests can only provide an average of alcohol consumption over approximate 3 or 6 months periods. Therefore they can be a “blunt instrument” when trying to establish changes in the pattern of alcohol use (increasing, maintenance of, or decreasing use).
Below is an example of the issues that can arise from using hair tests alone:
- Client A drinks very heavily, over 100 units per week and subsequently stops or significantly reduces their drinking for the 6 to 8 weeks prior to testing.
- Client B drinks excessively at around 60 to 70 units per week for the entire period of 12 or more weeks up to the point of testing.
- Client C has been teetotal for several months but relapses and begins drinking heavily again, over 100 units per week for around 5 to 6 prior to testing.
- Client D drinks at a dangerous level of >150 units per week, has for many years and is entirely dependant on alcohol.
Despite the very different drinking profiles these clients would generally produce the same Positive EtG and FAEE results and it would not be possible to differentiate one from the other. Clearly these are very different patterns of use, resulting in different recommendations and outcomes. Combining the use of blood markers, which can react quickly to changes in alcohol use, enables the Expert to differentiate between these profiles and provide appropriate recommendations to help the courts come to the right decision.
EtG and FAEE can provide different answers
- FAEE and EtG are different with regards to their methods of incorporation into the hair, stability and distribution along the hair shaft, therefore these markers have different sensitivity and specificity profiles. FAEE migrates along the hair shaft away from the scalp over time concentrating in the older hair, EtG tends to be higher in recently grown hair, and therefore recent periods of reduced alcohol use or abstinence can cause the FAEE levels to fall more quickly than EtG, which can cause a discrepancy in the FAEE and EtG results in around 20% of cases.
External influences can produce misleading results
- Hair is exposed to various external, environmental and genetic factors that can influence the presence or absence, or the levels of FAEE and/or EtG found in the hair. Different types of hair treatments and the frequency with which they are used have been shown to have a significant influence on the levels of either FAEE and/or EtG, causing the results to be understated or overstated, which, in the extreme, can give rise to False Positive or False Negative test results.
Furthermore these treatments affect EtG and FAEE very differently and therefore testing both markers is usually recommended particularly in women to provide a more reliable outcome. However even with the results of both EtG and FAEE it is important that they are interpreted in the context of blood test results, which are not exposed to the same external influences.
Scalp hair not always available or of sufficient length
- Certain individuals do not have any scalp or even body hair for testing and scalp hair is not always long enough to provide the optimal 3 cm sample for EtG or the mandatory minimum 3 cm sample for FAEE testing, which is required for optimal results interpretation.
Summary - Because of the various issues described above, there are conflicts between FAEE and EtG results in more than 20% of cases leading to uncertainty. These conflicts can often be resolved by putting the results into context with the blood test results. Without the blood test results, in a significant number of cases, the results would remain inconclusive and no progress could be made without further testing, with the resulting wasted costs and time.