Blog - Hair testing guidelines – how do we manage without an Australian Standard?

Scientist with hair sample

Hair testing for drugs is an approach that has significant advantages for particular investigations. Head hair grows at roughly one centimetre per month and the window of detection of drugs depends on the length of hair available. This can include the period approximately 2 weeks to 6 months prior to testing.  This testing regime complements the use of urine drug testing (detecting drugs over a period of about 6 hours to one week prior) and oral fluid test (detecting from several minutes to 3 days prior).

Hair testing can be particularly effective in cases where;

A broad history of drug use is required (e.g. for Family Court and child custody matters, for security and safety sensitive occupations, where drug and alcohol abstinence is required to be confirmed)

  • forensic analysis may reveal a history of intentional or unintentional drug exposure
  • clinical decisions are based on drug exposure history
  • oral fluid or urine collections are difficult (e.g. when investigating exposure of children and infants)
  • populations are being examined for drug availability and use patterns (e.g. Correctional Services testing of prison populations).

When a drug concentration is determined from any hair sample, expressed as a quantity of drug per weight of hair tested (e.g. pg drug/mg hair[1]), it cannot be interpreted in isolation. It means only that drug exposure has occurred that is detectable by the methods of testing used by the laboratory. There is a poor association between blood drug concentrations and the concentration achieved in hair, and we can only say that more drug in hair represents greater exposure. Strictly speaking, we need some standard or guideline with which we can compare hair drug concentrations so that we can draw appropriate conclusions.

When we conduct urine or oral fluid drug testing, we compare our test results with threshold concentrations (known as cut-off or target concentrations) specified in Australian Standards (AS 4308 and AS/NZS 4760 respectively). These threshold concentrations indicate a level at which drug exposure is confirmed and that may indicate occasional or ongoing drug (or medicine) use. This enables decisions to be made regarding fitness for work consistent with well-designed workplace drug and alcohol policies. If workers exceed these specified thresholds then they may be subject to sanctions up to and including termination of employment.  Workers whose drug test results are below these thresholds are considered effectively drug-free for the purposes of drug and alcohol policies.

When conducting hair drug analysis, there is no Australian Standard that applies. The Society of Hair Testing is an international  organisation whose goals are

  • Promotion of research in hair testing technologies in forensic, clinical and occupational sciences,
  • Development of international proficiency tests,
  • Organization of meetings and workshops, and
  • Encouragement to scientific cooperation and exchanges among members.

The Society publishes Guidelines for best practice in the collection and analysis of hair specimens, and also publishes cut-off concentrations that identify use. Specifically, the cut-off concentrations refer to chronic use of drugs and may be applied to

  • drug-related deaths,
  • drug-facilitated crime,
  • child custody, and
  • chronic excessive alcohol consumption.

It is important to note that workplace drug testing is not specifically identified as an application of these cut-off concentrations. The Guidelines specify that in some applications where single use or exposure to drugs is investigated (such as in drug facilitated crime, and by extension, in workplace drug testing programs), a lower cut-off should apply. In practice, individual laboratories will develop their own specific tables of cut-off concentrations based on their specific analytical instrumentation and methods, and to levels as low as their Limit of Quantitation. In this way, workplace cut-offs are presented by each laboratory that indicate casual or occasional drug use that may apply to workplace drug and alcohol policies.

When a worker is detected with a confirmed positive drug test using urine of oral fluid, the respective Standards specify mechanisms by which workers may dispute their confirmed test results. This is enabled by the collection of a “B sample” (either an aliquot of the original urine specimen split at the time of collection or a second oral fluid sample collected at the same time as the original) that is available to a laboratory of the donor’s choice to be tested for consistency with the original confirmation laboratory.  In the cases of urine and oral fluid, the dispute (B sample) laboratory need only detect the drug of interest and it is not necessary to exceed any cut-off or target concentration.  However, for hair analysis, any sample that is collected that is confirmed by the laboratory to contain drugs exceeding either the Society of Hair Testing or laboratory cut-off concentrations (whichever applies in the workplace policy) and which is to be disputed (via a B sample), MUST be analysed by a laboratory with a limit of quantitation at least as stringent as that of the original laboratory. That is, a laboratory that cannot meet the analytical precision and accuracy of the workplace policy cannot be eligible to be a B-sample analysis laboratory.

Although the procedure described above for hair is reasonable and defensible, the absence of an Australian Standard to support its implementation is a barrier for some businesses contemplating the use of hair analysis as a drug testing strategy. It would be preferable to develop an Australian Standard for hair analysis, or at least encourage the Society of Hair Testing to offer a set of differential cut-off concentrations for different applications (including workplace drug testing). We live in hope.

Boilerplate John

[1] pg is picogram – one million-millionth of a gram (10-12g); mg is milligram – one thousandth of a gram