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The long- established and well-trodden path of drug and alcohol testing hair samples is currently being challenged by the relatively newly-developed methods of testing nails for similar substances.

Is the analysis of nails the future of drug testing and will we see a decline in traditional hair testing methods?

Hair drug and alcohol analysis has been around for many years and the results are supported by standards, Society of Hair Testing guidelines for drug testing in hair, recognised cut -off levels and UKAS ISO17025 accreditation, which give the methods and results credibility for use in numerous arenas including the Family Courts.

Analysis of drugs in fingernails and toenails – is it an alternative to hair?

Hair and nails are both formed by keratin, the fibrous protein which traps drugs and alcohol biomarkers.  As the nail grows, substances can pass from the blood vessels below the nail into the keratin fibres where they become trapped and biomarkers from the substances can be detected in the nails. Therefore, both hair and nail testing can be used to detect the same things. However, hair and nail sample types, when being tested for the same drugs and alcohol biomarkers may produce varying test results and as there is limited information and no industry-wide standards or agreed cut-off levels for nails, it is wise to be cautious of the results, as interpretation can be difficult and easily challenged.

Head hair samples can be segmented for drug testing to provide a month by month analysis of the donor’s drug usage for a period of up to twelve months after use, whereas nail clippings cannot. Nail clippings can be used to detect drugs for up to 6 months after use, but can’t be segmented so can only give an overview rather than the pattern of drug use which head hair can show.

In the same way that head hair and body hair samples can’t be mixed together as they have different growth rates, nor can fingernail and toenail samples. Even when a 2-3mm sample from all ten fingernails is collected, there is often insufficient sample to test for a large panel of drugs and the method relies on the donor have sufficient nail samples to be clipped.

The detection of alcohol abuse using head hair samples is well documented and EtG (Ethyl Glucuronide) and FAEE (Fatty Acid Ethyl Esters) alcohol markers are readily detectable and quantifiable in the samples. It is strongly recommended within the industry that the two sets of analysis are run side by side and that one is not reported without the other as they can provide conflicting information. The limited research which has been conducted on nail samples provides information about levels of EtG alcohol markers which are trapped in the nail as it grows but does not provide information about FAEE markers. Caution is required, as the two sets of results should always go hand in hand.

Hence, we can see that nail drug testing has limited uses and should only be used as an alternative to hair testing if the donor has no head and limited body hair. However, due to a lack of vital controls, the results should always be viewed with caution.