Advantages of hair testing
Drug testing using hair shows what drugs have been used over an extended time frame of months rather than days, which is the time frame associated with urine and saliva (oral fluid) testing.
Hair testing is much more sensitive to occasional and intermittent drug use. Where urine testing might miss a “party habit” every two weeks, hair testing will not. It is this much improved confidence of detection that established the value of hair testing in Children at Risk cases.
Pattern of drug use from hair testing
When the hair sample is sufficiently long, multiple sections can be tested. Each section then represents blocks of several weeks and any changing pattern of drug use may be revealed, by detecting increasing or decreasing levels over longer time periods.
Can we tell the amount of drug used?
We believe that providers of hair testing services have the responsibility to supply their clients with clear and accurate information on the potential advantages of hair testing and also with its limitations.
For example, the levels of drugs detected in hair are best used as a guide to changes of use in the individual when sectional analysis is performed or two different periods are compared in the same individual.
In an individual, one may assume that high levels detected in a hair sample reflect high use, however, this assumption can be misleading. The testing laboratory is only able to give an indication, based on the cumulative results of its testing experience, of the levels detected in comparison with others, but cannot be sure about the quantity used.
This is because hair colour can markedly affect the level of drug taken up in hair strands. So a couple following the same pattern of drug use, including dose, can show remarkably different levels of hair drug levels if one is fair- haired and the other dark haired.
In cases where no head hair is available, body hair may be used but the time scales are much less clear. In effect any drug found in body hair is ‘smudged’ over a much greater time-window. Whilst body hair cycle can have longer window of detection in comparison to head hair, it can only cover 365 days if the sample of body hair at least 6 centimetres long. This is seldom true.