Toxicology
Testing
Toxicology Definition
"The study of the nature, effects, and detection of poisons
and the treatment of poisoning."
Overview
The use of illegal or illicit drugs is known to have a serious
effect on workplaces across all industry sectors so sound drug and
alcohol policies are put in place supported by expert testing for
substances of abuse. Accidents caused by impairment due to drugs or
alcohol can result damage to products, buildings and vehicles but
more importantly, lives.
A positive drug result can have serious consequences for all
involved, so it is important that every stage of workplace testing
is carried out by experienced, qualified and professional
organisations.
The United
Kingdom Accreditation Service, (UKAS) accredits specific methods
and processes so a laboratory holding UKAS
accreditation will test to accepted, regularly audited
standards – assuring clients of the quality of both the service
levels and results that they receive.
Testing should be carried out to the relevant guidelines which
may be SAMHSA, (The Substance Abuse and Mental Health Services
Administration), or UKWDTC, (UK Workplace Drug Testing
Committee).
The laboratory analysis at SHLS for drugs of abuse provides a
legally defensible result – the sample donor is linked through an
audit trail to the final test result. This audit trail is
known as the chain of custody.
The chain of custody requires that two identical samples are
provided, (A and B) so that one sample remains intact should the
sample donor wish to challenge the initial result. The A
sample is analysed using an immunoassay (primary screen) and this
gives a presumptive result. Negative samples at this stage
are reported as negative. Positive samples are further
confirmed using the reference method – GC-MS or LC-MS, which
provides a legally defensible result. Futhermore other services
SHLS can provide customers include expert witness statements and a
Medical Review Officer.
Urine Testing
Urine testing remains the mainstay of drugs of abuse
testing as the sample is easy to collect and analyse, with
reasonable timescales for drug detection. Although there is a very
slight possibility of adulteration or substitution of samples the
strict collection procedures
used by
SHLS for many years have proved that the process is well controlled
and results will be legally defensible. Issues such as
passive smoking and cross-reaction of other substances have been
well-researched over many years and working to the relevant
guidelines, SHLS ensures that all tests are run with appropriate
cut-off levels to ensure that there are no false-positive or
false-negative results.
The retention time of drugs in urine is mostly between 2
and 4 days, meaning that it is a good method for most types of
workplace testing providing a 'snapshot' of donor status. It
can be useful in random testing or pre-employment testing schemes
in particular.
Oral Fluid / Saliva Testing
There is no technical difference in this fluid – whether termed
saliva, oral fluid or oral mucosal transudate.
This is a relatively new matrix for testing drugs of abuse, but
is finding favour in some quarters. Technically it is more
difficult to test than urine as drugs are present in much smaller
quantities and the amount of fluid available for testing is much
smaller. This can mean issues with collecting A and B
samples, but the UK Workplace Drug Testing Committee, (UKWDTC), is
currently producing guidelines on the management of B samples so
chain of custody procedures are superior to those available 5 years
ago. Methods of analysis have also improved and in SHLS'
laboratory, the analysis of saliva is carried out swiftly and
effectively to UKAS standards.
In order to obtain a valid sample, the fluid must be carefully,
passively collected, with no change to pH or use of chemicals to
draw out fluid as this affects the sample analysis.
Saliva mimics blood levels of drugs and can therefore provide a
more immediate, (snapshot), of donor status than urine.
Retention time of drugs is generally 24-36 hours so this method may
be useful, particularly in 'for cause' or 'post incident'
testing.
Hair
Hair testing is an accepted procedure for assessing drug use,
especially over long periods. It is quite invasive as the
amount of hair needed is usually about 3cm and the thickness of a
pencil. Analysis can be carried out on 1cm segments to define
specific periods of drug use. Normal hair grows at between
0.7 and 2cm per month; drugs reside in the hair shaft at
a point related to the drug use. This means
that occasional use will affect only some parts of the hair shaft,
whilst ongoing use will leave drug residues in the whole hair
shaft. It takes 1-2 weeks for the drug to reach the hair from
the body (via the hair follicle), so there is a significant time
lag in appearance of the drug in the hair shaft.
It can be difficult to collect sufficient hair and occasional
users might be missed as the levels of drug in the hair can be very
low.
Analysis of hair for drugs is useful in legal cases (paternity
and custody cases), long term assessment of drug users on
rehabilitation programmes, or possibly for random or pre-employment
testing.
Confirmation
Testing for drugs is normally a 2 stage process. The
first test is based on antibodies to groups of drugs, which will
quickly give a negative result if no drugs are present. However,
this test is non-specific, and cannot tell the difference between
some Over-the Counter medicines and illegal drugs, which is why we
do not say that a screening result is "Positive". Any result that
is non-negative is therefore sent for confirmation to prove that
the drug is present, and also find the amount present.
The confirmation processes in use at SHLS are based on Gas or
Liquid Chromatography with mass spectrometric detection (GC-MS and
LC-MS). The chromatography separates the different substances in
the urine so that they can be detected at different times, and the
mass spectrometer selects drugs of a particular mass, fragments
them, and then isolates the fragments and determines how much is
present compared to a known standard. The quantities that must be
present to report a drug as positive are based on nationally or
internationally recognised threshold values. The GC-MS and LC-MS
processes are highly selective, and ensure that we can detect the
drugs without interference from medicines or diet. These methods
are extensively validated and tested to make sure that the results
are accurate, and your workplace remains drug-free.
Expert Witness Service
SHLS can provide expert witness statements to
companies if required, our expert toxicologists have vast
experience in the field of drug testing and function at doctorate
level. A fully written report or statement can be issued for use as
evidence in the court of law or investigations. Alternatively one
of our senior toxicologists can attend a court hearing in person to
give an expert witness statement. Toxicology testing is required
for a number of reasons varying from road traffic accidents to
probation cases, the experienced staff at SHLS combined with our
unrivalled quality accreditations ensure the highest standard of
service is delivered to our customers.
Medical Review Officer
The field of toxicology testing in the
workplace does not always reveal a straight answer; occasionally
employees may work whilst on prescription medication and be
completely work safe and legal. SHLS offer a fully qualified
Medical Review Officer to investigate, review and offer
professional advice to employers regarding individual situations,
ensuring a definitive conclusion is established in each case.
Click here to contact us for more
information regarding any of the services listed.