Workplace Drug Testing: Different Matrices Different Objectives

John Wicks & Lolita Tsanaclis

Cansford Laboratories Limited, The Cardiff Medicentre, Cardiff, UK
The Cardiff Medicentre, Heath Park, Cardiff, CF14 4UJ
Tel: 029 2068 2031

Drug testing is used by employers to detect drug use by employees or job candidates.  It can identify recent use of alcohol, prescription drugs and illicit drugs but it cannot detect impairment.  So such testing should be used as a screening tool for potential health and safety and performance issues.

The use of drug testing in the Workplace requires a clear, written policy that is discussed and agreed with all employees before testing starts.

Urine is the most commonly used sample for illicit drugs. It detects the use of a drug within the last few days and as such is evidence of recent use; but a positive test does not necessarily mean that the individual was impaired at the time of the test.  And abstention from use for 3 days will often produce a negative test result.

Analysis of Hair provides a much longer window of detection, typically 1 to 3 months.  Hence the likelihood of a false negative test using hair is very much less than with a urine test.  Conversely, a negative hair test is a substantially stronger indicator of a non-drug user than a negative urine test.

Studies have shown that within the same industrial settings hair testing can detect 10 times more drug users than urine testing. Like urine testing, hair testing does not provide evidence of current impairment only of past use of a drug.  But hair analysis can indicate frequency of use.  Hair testing has no privacy issues as it is a non-invasive technique.  The sample is taken under observation and is much less liable to be substituted than a urine sample.

Oral Fluid or Saliva is also 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.  So the method is a good way of detecting actual current use and is more likely to reflect current impairment.  It offers promise as a test in ‘post-accident’, for cause, and on duty situations.

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.

Published in Spring 2011

Posted in Did you know?, Editorials