Behind the scenes of a hair drug test: What really happens in the lab

James Nutt

James Nutt

on Jul 19, 2016

FAQs_-_image_for_pageThe hair sample has been taken and is on its way to the lab. For donors, it’s now a waiting game to see the outcome of the analysis. But what exactly is it a drug testing lab does to detect drug and alcohol use in just a few strands of hair? 

In the space of a couple of days, labs can do a drug test with hair and reveal a donor’s drug use dating back months. The reports labs produce evaluating drug use can be extremely accurate, measuring drug use right down to the picogram level.To give you an insight into just how labs can do this, we’ve outlined the process laboratory’s go through to prepare a hair strand test for alcohol or drugs when assessing drug and alcohol use.


Booking in the sample

When the sample arrives in the lab, it has to be thoroughly checked for any signs of tampering while in transit. If a sample collector from the lab took the sample from the donor, the sample should be packaged with a tamper-evident seal. In the lab, a technician can then check the seal for any signs of tampering. 

Once the integrity of the sample has been given the all clear, the sample is booked into the labs information management system (LIMs), recording who the donor is and what drugs need to be tested for. Eventually, the sample can move on to the first stage of preparation.

The hair sample is cut (or isn’t) 

One of the first preparations a lab will do is align the sample. This involves identifying which end of the hair sample was rooted in the scalp. Essentially, the root end of the sample is aligned to represent the point referred to as ‘0 centimetres’. 

Labs will measure out hair samples in centimetres, as hair tends to grow at roughly 1cm per month, with each centimetre reflecting 1 month’s history of drug use. So a 3cm strand of hair is kind of like a diary of drug use over the last 3 months.

Identifying which end of the hair is rooted in the scalp is vital to interpreting the results accurately. This is because sections of the hair strand closest to the scalp indicate recent drug use. If labs get this the wrong way round, drug use 3 months ago could be misinterpreted as having occurred 3 weeks ago. 

Once the sample is aligned it’s then cut, if necessary, according to the client’s request. In the lab, this is called ‘sectioning’ i.e. cutting the sample into three, 1cm sections.

By ‘if necessary’, this is based on whether the client has requested overview or sectional analysis, but also the length and type of hair.

Sectional testing is where the hair sample is cut into 1 centimetre sections (or less depending on the purpose of the test) and each section is separately analysed for drug use.

Sectioning is also influenced by the length of the hair and the hair type. For example, body hair isn’t suitable to be cut into separate sections, so the full length of hair is analysed.

If a 1cm sample of head hair is received, but the requested period of analysis is longer than 1 month (remember, 1cm = 1 month’s drug history), there is no need to cut or ‘section’ the sample.

Because sectional testing analyses hair in individual 1cm sections, labs have the ability to say “actually, the level of cocaine has decreased in the sections representing April and May, but was not detected in June”.

With overview testing, the whole length of hair requested for analysis is analysed as one portion. What this means for analysis is the lab will be able to assess any drug use over the previous months (depending on what’s requested), but they won’t be able to tell in which of those months’ drug use specifically occurred. The result is an integrated average of the time period represented by the analysis.

In any case, whether it’s overview or sectional testing, once the hair has been cut (or not), it’s placed into a test tube or series of test tubes that are barcoded. This enables the lab to track the hair sample throughout the lab and see exactly where it’s come from and where it’s going. 

The hair sample is washed 

Before a drug test with hair can take place, the hair needs to be washed. Labs do this for two reasons.

Firstly, washing prevents any wax, cream, dirt or shampoo from making its way into the testing instruments. Secondly, washing the hair sample removes any drugs that might have become trapped on the outside of the hair by external contamination. 

This is extremely important, as some donors may not actually have used any drugs, but may live in a house with other people that do. This is also useful in workplace testing. For example, Police Officers who work a lot of drug cases tend to handle large amounts of drugs or raid houses where people are using drugs.

Washing the sample removes these types of external contamination, eliminating the possibility of interpreting drug use when actually, there hasn’t been any. 

Just to be on the safe side though, once the hair has been washed, the residue is kept for analysis. This allows the lab to do a comparison between the hair sample itself and wash residue, so they can confidently conclude whether the donor actually used any drugs.

After the sample has been washed, it can move on to the next stage. 

The hair sample is analysed using LC-MS/MS

After washing, the lab will use chemical and mechanical techniques to disintegrate and dissolve the hair, producing a liquefied hair sample ready for analysis.

This liquefied sample can be analysed using LC-MS/MS, which stands for Liquid Chromatography with Mass Spectrometer in tandem. Basically, LC-MS/MS separates any drugs within the sample and identifies exactly what they are i.e. cocaine, heroin etc. 

By weighing the hair sample, labs can then tell what quantity any drugs are present in, giving an indication of a donor’s drug use.

Once the analysis is complete, a Certificate of Analysis is produced which outlines what the lab found and in what quantities.

So that’s a behind the scenes tour of what happens in a drug testing lab when they conduct a drug and alcohol test on a hair sample. But just as a reminder;

  • The sample is booked in along with who the donor is and what drugs are being assessed.
  • The hair sample is cut or not, depending on whether sectional or overview testing respectively, will be used.
  • The hair is washed, disintegrated and the liquefied sample is tested for the presence of drugs.

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James Nutt

James Nutt

James Nutt is Cansford’s Senior Reporting Scientist and Laboratory Manager. He has extensive knowledge and experience of toxicology in relation to family court, reporting and drug and alcohol testing.

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