FAQ

How accurate are drug tests?


Providing the sample is genuine, a competent laboratory performs the analysis and the sample is both screened and confirmed, the chances of a 'false positive' are very slim. Screening, the first stage in testing, sometimes does not differentiate between drugs available over the counter and illicit drugs from the same drug group. But a positive result from a screening goes on to a second-stage confirmation test, using Gas Chromatography/Mass Spectrometer analysis or similar, and the result is of 'fingerprint' accuracy - clearly defining which drugs were detected in the sample. Top



But what about external contamination?


TrichoTech washes the hair samples prior to testing as an additional safeguard for donors. Even if donors spend a lot of time with other people who smoke or take illicit drugs, the GC/MS technique tests for metabolites, specific compounds of drugs that are found only once those drugs have been ingested. Top



Which drug test should I use? How do I decide which is best for my company or organisation?

Decide on what the purpose of the tests is - is it to check new recruits are not bringing in a drug problem with them? Or to ensure an operator is safe to drive or run machinery there and then? There may be a combination of reasons - and you may therefore need a combination of test methods at your disposal. Remember that most test kit suppliers have one range of products, so they focus on their advantages - laboratories like TrichoTech test and confirm samples from major oral fluids and urine kit providers. So as well as offering hair analysis, we can provide an expert opinion on the test programme that best fits your purpose. Our company policy is to be honest about the limitations of each sample type and method - none of them are perfect - so you have the information with which to make the decision. Top

When should I choose a hair test instead of urine or oral fluids?

  • When you need a window of detection that stretches back beyond 2-3 days.
  • When you want to be certain about drug use or abstinence - hair tests are 5-10 times more sensitive than urinalysis.
  • When you would like to monitor a person with a known drug history over a period of time, but don't want to be taking tests every two or three days.
  • When a urine test is not acceptable for reasons of dignity.

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When should I NOT choose a hair test?


  • When you need to know if someone has taken drugs in the last 24 hours - 3 days.
  • When you need a continuous timeline of drug use measured in days not in months.

Analyse one section of hair, say 3cm long, and that provides a picture of someone's drug history over approximately 3 months - not a weekend or a particular day that drugs were taken. You can define the likely month the drug was taken by analysing each centimetre of hair separately. Top

I have read that cannabis cannot be detected in hair. Is this true?


No. Cannabis is certainly more difficult to detect in hair but for some years TrichoTech has been developing techniques that have steadily increased the sensitivity so that we can now reliably determine the presence of cannabis constituents in hair. We test for three constituents of cannabis. These are tetrahydrocannabinol (THC), Cannabidiol (CBD) and Cannabinol (CBN) and we also test for two further metabolites of THC, that is 11-hydroxy-delta9 THC and 11 nor-delta9-THC-9-carboxylic acid. These latter two metabolites are converted from THC after cannabis has been consumed and are therefore markers of actual consumption whereas the finding of THC, CBD and CBN can only prove an association with cannabis. Increased concentrations can indicate that active consumption is more likely than passive smoking. Top



Will the use of chemicals on hair affect the results?


Chemical treatment of the hair such as hair dye, bleach, chemical straightening and permanent waves can damage the hair. This damage may lead to some of any drugs that may be present, being leached out from the hair, therefore treated hair may hold less drug than if the hair had not been treated. As a result, it is possible that low or single use of any drugs may not be detected. More frequent use of drugs can still be detected but the concentration found may be less than that detected in untreated hair. Top

How much hair is needed for a test?


About 50 strands are required from the head, about the width of a thin pencil, or the tip of a shoe lace. There are approximately 100 000 strands of hair on average on a person's head, so this should not make any cosmetic difference, unless the hair is very short (see below). Top

What if the donor has little or no head hair?


Even shavings from a very short ('number one') haircut can be tested, for a profile of drug use of about a week. If the donor has no head hair then hair from other parts of the body can be analysed - beard, armpit, chest or pubic hair. Someone who has shaved their head prior to a test can therefore still provide a sample. If the donor objects or has shaved all body hair - well, they can be offered the alternative: observed urine tests twice weekly for 3 months! Top

What is the time period a standard test covers, and what variations can I request?


The most common test requested is for a 3 months/90 day history or profile of drug use or abstinence, requiring a 3 cm (1 ¼ inches) length of hair sample. We can, however, test from less than one centimetre up to any length of hair sample available, though we have to cut long samples into maximum 3 cm length sections, to maintain the test's sensitivity. Drug use profiles are therefore available from approximately 7 or 8 days history through to over 2 years.

TrichoTech has provided clients in medical-legal fields with 2-year profiles on a number of occasions for donors with hair 24 cm in length. Testing a centimetre at a time is more expensive but will provide a month-by-month history, especially useful when assessing progress of treatment or when a more precise view of when drug use occurred is required.Top


Do hair tests discriminate between fair haired and dark haired people?


No. It is a scientific fact that dark hair can take up more of some drugs than fair hair, but the differences are very small. Large population studies of hair testing have shown that there is no racial or colour bias when urine and hair tests are compared side by side. For example, a very large cocaine study published in January 2001 considered over 56 000 samples and found no significant relationship between hair colour and likelihood to test positive. Our own experience testing over 15 000 hair samples is similar; we examine and record the colour of each sample. Results from hair testing provide a higher degree of accuracy about drug use or abstinence than urinalysis. Factor in the large potential for fraud and evasion of urine testing, not forgetting the 'dignity' element for the donor, and hair analysis remains a powerful, safer choice for the testing and treatment of drug addiction. Top


What about civil liberties?


There are many medical and legal reasons why drug tests are carried out, but there is an increasing use of testing in the workplace too, and this has rightly generated considerable debate on civil liberties. Testing for drugs in the workplace should be part and parcel of a drugs and alcohol policy, agreed between management and staff - it is after all in both parties' interests not to have a health, safety, criminal, or performance-related risk present at work but ignored. All tests for problem drug use should be taken with the donor's consent. Finding the balance between an individual's right and social behaviour and the need to protect people from possible harm to themselves or others is important. Neither the issue of civil liberties nor that of problem drug use should be ignored - models of good practice that show that appropriate solutions can be achieved should be made widely available. Top


What studies have been published on hair testing?


The regular monitoring of drug users by the use of hair analysis started with an article in a medical science journal in 1979. Since then over 400 papers have been published on the use of hair analysis in Forensic Science International, The Lancet, British Journal of Psychiatry, Therapeutic Drug Monitoring, Journal of Analytical Toxicology, International Journal of Legal Medicine, European Journal of Clinical Pharmacology, American Journal of Drug and Alcohol Abuse, International Journal of Drug Testing, Journal of Forensic Science, Clinical Toxicology, Journal of Pharmaceutical Science, New York Academy of Medicine, Folio Pharmacologica, Japonica. Top

Can passive smoking have an effect on results?

It is extremely unlikely that a positive drugs test could be the result of passive smoking. Smoke from drugs inhaled by a non-drug user can deposit small amounts of that drug in their system but this is far below the cut-off levels we apply to our results in order to protect the donor from such a possibility. The hair samples are also washed prior to extraction to eliminate any environmental contamination. Top

How can you detect the difference between over-the counter drugs and illegal substances?

As an example, Heroin and Codeine (an over the counter remedy) have different molecular masses and different chemical structures, so they both travel through the GC-MS analyser at different times. The analyst will identify the illegal drug from the over the counter drug, by looking at the time drugs took to travel through the GC-MS analyser and its chemical structure. Each drug has its own unique chemical structure which is then used to identify the drug. Top