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Segmented or Overview?

An overview analysis provides an ‘average’ of a number of months grouped together. For example, if you simply want to know if someone has taken drugs within approximately the last three months, we would analyse a single 3cm section of the most recent hair growth. Because this is a single sample it is very cost-effective. If the result is positive for a drug or drugs, this will indicate usage during the months prior to sampling but we would not be able to tell you in which of the three months the drug(s) had been taken. Overviews may also not detect low level or infrequent irregular use, as these would be potentially ‘diluted’ within the time period we are investigating.

By segmenting head hair samples into monthly 1 cm sections, a month-by-month historic profile of drug use can be obtained. For example, if someone has reported that they took drugs 6 months ago but has not taken any since, this can be explored by taking a 6cm section of hair and cutting into 1cm sections. We would then analyse each as its own separate test and report the results for each section to provide a picture of any drug use over this period of time.

If no head hair is available for testing, we can of course analyse body hair. However, the variability in the growth rate of body hair means that we can only reliably provide an overview analysis of recent drug use, rather than segmental testing.

Testing individuals under the age of 18

When we receive hair samples from children some additional testing and interpretation is required.

Hair from children is finer and more porous in comparison with adult hair and, therefore, it is more prone to external contamination from drug usage in a child’s immediate environment. As a result, washing the hair sample or section will remove or minimise any external contamination that may have been present on the surface of the hair. However, it may not remove all of it. This is where ‘washes’ can provide more information.

By looking at a comparison of any drugs present in the hair sample verses what is present in the ‘wash’ it can provide bigger picture of exposure and/or ingestion.

For child cases, this additional information is vital in order to understand and provide an interpretation of the findings.