Which sample to use in drug testing?

Nowadays the use of the three biological samples, urine, saliva and hair, is widely accepted for the detection and monitoring of drug use. They are complementary and each sample type has different advantages depending on the purpose of the test. There is not a best sample for drug analysis, just the ideal sample for a particular purpose.

Time frame or window of detection

Analysis of hair provides a much longer window of detection, typically 1 to 3 months as drugs and other substances remain fixed and trapped in the hair indefinitely after they are incorporated in the hair after drug use.

A negative hair test is a substantially stronger indicator that someone does or does not use drugs than a negative urine test, as it shows drug use, or absence of drug use, over a longer period. It can also indicate frequency of drug use.

Hair test reveals 3-4 times more drug users then urinalysis.

Drug testing can provide a screening mechanism for new employers as well as a deterrent for existing members of staff.window

Urine and saliva shows what drugs have been used for a relatively short period, in the hours before sample collection (24-72 hours depending on the drug). In contrast, hair provides information of use over a much more extended period of the order of weeks or months. Abstention from use for 3 days will often produce a negative test result in urine but will be picked up in hair.

For the purpose of testing for safety in the workplace or testing vehicle drivers, tests utilised are usually on-site tests using urine or saliva, which provides a ‘short window’ of detection and a test that shows there and then whether a person has been taken drugs (including alcohol).

Sample Collection

Different materials also differ in how the samples are collected. The collection of hair is simple, non-invasive and dignified.

There has also grown up an extensive knowledge of the ways drug users can subvert a urine testing and the collection is considered invasive of a person’s privacy and undignified.

Oral Fluid or Saliva is easy to collect.  The most usual method is with a swab placed in the mouth that collects a sample of fluid for testing.  Drugs remain in oral fluid for a similar time as in blood (about 24 hours).  So the method is a good way of detecting actual current drug use and is more likely therefore to reflect whether functioning, such as driving, is currently impaired by drug use.

Although Urine has some advantages such as the ease of detection, the availability of on-site immunoassay kits that enable rapid screening and the extensive amount of information available on use and interpretation of the testing, hair has many advantages because of its long window of detection and ease of sample collection.

Typical characteristic




Window of detection(*)

1 day

2 – 4 days


Length of abstinence from drugs to produce a negative result(*)

24 hours

2 – 4 days


Invasive collection




Risk of sample adulteration




(*) It depends on the drug, dose and frequency of use

It remains essential in all cases to combine drug testing with a clinical appraisal of the actual behaviour of the individual, before coming to any conclusion as to what action may be appropriate.

Posted in Hair drug testing, Oral fluid testing, Workplace Drug Testing Tagged with: , , ,