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Drugs and Alcohol in the Workplace – An Introduction to Getting it Right

By Matt Taylor, Innovative Testing Solutions Ltd

Published 28 July 2022

Featured image drug and alcohol post

Why do organisations / companies test?

Drug and alcohol testing in the workplace has been commonplace in the UK for over 20 years now. It became “mainstream” within the Rail industry following the Cannon Street rail crash of January 8th, 1991, which killed 2 people and injured (some seriously) 542 others despite happening at only 10 mph. It was found that the driver of the train had failed to brake properly, causing the crash. The driver was also found to have cannabis in his system. Following this, many other industry sectors have realised the benefits of managing the risks of Drugs and Alcohol in the workplace both for safety critical and business critical reasons.

What people do in their own time is not usually the concern of their employer. However, when they enter the workplace – wherever that may be – it becomes the concern of the company or organisation that is responsible for their Health and Safety amongst other things.

Drug and alcohol testing in the workplace is therefore done primarily to improve health, safety and welfare within the work environment. In many situations, people who are under the influence of drugs or alcohol at work will put themselves and others at considerable risk.

There are many other reasons that companies and organisations may carry out drug and alcohol testing. A robust and legally defensible Policy and Procedures (including support) together with the right training, education and drug and alcohol testing program can help your company:

  • Avoid employing or engaging individuals who may pose a higher safety risk.
  • Investigate accidents, incidents or near misses and rule in/out drugs and alcohol as being a contributing factor.
  • Investigate and answer any allegations of information about sites or specific employees around substance misuse.
  • Identify employees who may have developed substance misuse problems and help them seek help, recover and return to the workplace safely.
  • Collect data to reduce organisational risk and liability.
  • Assure and retain responsible employees who value health, safety and welfare.
  • Demonstrate corporate and social responsibility to the communities you work within.
  • Reduce accidents and incidents due to drug and/or alcohol use – including “morning after” and “hangover/comedown” periods drug and/or alcohol use.
  • Reduce absenteeism and presenteeism following drugs and/or alcohol use.
  • Give Directors, Managers, Supervisors and all Employees clear and concise guidelines of what is/what is not expected of them leading to a more timely and consistent intervention as and when required.
  • To win valuable contracts (“compliance”) and to meet some specific insurance cover requirements.
  • Comply with specific industry regulations and legislations.

There are various situations when drug and alcohol testing can be done. Depending on the goals and the requirements you have to meet, you might want to do testing in all or some of these situations. The most common reasons for testing are:

  • Pre-employment testingTo identify candidates who could pose a risk to the business / other employees etc.
  • Site Induction testing To identify people who could pose a risk before giving them access to a work site (may include visitors and contractors etc).
  • For Cause testingTo determine possible contributing factors of a workplace accident, incident or near miss and to help prevent future incidents.
  • With cause testing: Following up on information or when there are visible signs and symptoms of substance use impacting upon safety and possible performance.
  • Random / Un-announced testingTo help ongoing deterrence of substance use and enhance safety policy compliance by regularly testing a random sample of the workforce.
  • Employee compliance / follow-up testingWhere an employee has come forward asking for help to ensure compliance with the Policy and return to work agreement.

Guidelines and Quality Standards

Drug tests should be performed in accordance with strict legal and workplace testing guidelines. In the U.K., it is standard practice to follow the EWDTS (European Workplace Drug Testing Society Guidelines) for the appropriate testing format. In addition to this, employers and Occupational Health (OH) services should always check for quality assurance and accreditations of both the products and services used.

For example, compliance to recognised quality standards such as ISO9001, ISO14001 and ISO17025 (for laboratory services) and also products that are “fit for purpose”, meet specific relevant “cut-off” levels (i.e., UK/European standards and not USA standards), carry CE (or soon to be UKCA) marking, meet IVDR (In Vito Diagnostic Regulations) if required etc. Only UK Home Office Approved breathalysers should be used where positive results may lead to disciplinary procedures.

Like anything in life, quality has a cost, and you tend to get what you pay for.

Two Parts to a Drug Test

There are usually two parts to a standard drug test. Most drug testing for workplaces is undertaken as a urine test or an oral saliva test and are broken down into these two stages:

  • Initial screening stage (qualifiable result – either a Negative, Non-Negative, or Invalid result with no measure of levels at this point), this can be a Near Donor Immunoassay (often referred to as a POCT or Point of Care Test) where the screening is carried out in front of the donor using an “instant/rapid” test and can be at the workplace.
    This is the initial test to find traces of drugs or their metabolites within the sample. Screening is not 100% accurate and is a qualitative result only (there is no definitive level found at this point – just that there has been a reaction or not). Think of it as the “Lateral Flow COVID test”. Initial screening procedures can include Laboratory screening methods (various) where you will need to wait for the result from the laboratory.
  • Where a screen result shows a “positive” (this should be referred to as a “non-negative” or “presumptive positive”) confirmation is needed and MUST be confirmed by laboratory analysis. The sample is subjected to analytical procedures such as GC/MS [Gas Chromatography/Mass Spectrometry], LC/MS [Liquid Chromatography/Mass Spectrometry] etc to both qualify and quantify the initial screen result. Think of this as the “PCR COVID test”. This is measured against any medication declared.

It is the Confirmation stage that is considered the ‘legally defensible’ result. You should not dismiss an employee or take definitive action based solely on the initial screen result. In an attempt to cut costs some employers or organisations will only use POCT drug screen results and not send “non-negative” samples to the laboratory for confirmation analysis. This will not give them a fully legally defensible result and therefore is not recommended as results are easily, and frequently, successfully challenged.

Many people refer to the laboratory and/or confirmation stage as a “Chain of Custody Test”, but it should be noted that “Chain of Custody” should actually be applied to every element of any drug test – even if the initial screening result is NEGATIVE and therefore does not require laboratory screening/confirmation. Collection officer/technician training and competency records, equipment calibration records, paperwork, donor selection, donor information, donor consent, sample collection techniques, results reporting etc. are all elements that make up what is actually the whole Chain of Custody process which is essential for supporting a workplace drug test.

Speed, Accuracy and Reliability of Initial Results with “for cause” testing

Getting a quick initial screen result is often paramount. Why? – because it is an immediate “risk assessment”. It allows you to make an informed decision about whether to remove a person from duties until the confirmation result is known. These initial results need to be as accurate as possible (all screening methods have a degree of in-accuracy) and reliable. Traditional screening of samples at a laboratory, mean initial results are not usually known for 24-48hrs. This means you have a very difficult decision to take:

  • Do I remove that person from duties until the initial results are known –usually on full pay?
  • Do I allow them to carry on with duties only to find out 48hrs later that they have possibly been working while “under the influence”? As a company – you may have therefore exposed them and others to further risk.

It is therefore more common to now use “Instant” or “Point of Care” screening devices within workplace drug testing unless the industry standard states otherwise for example Rail. These devices are highly accurate and reliable and can give an initial screen result in around 3-5 minutes. Paired with a breath test for alcohol using a UK Home Office approved breathalyser, an immediate risk assessment can be made by the employer/organisation without having to wait for laboratory screening results.

What Do Drug Tests Look For (“The Science Bit”!)?

It is important to understand that drug tests don’t just look for the actual drug itself, but often also the drug metabolites. 

Drugs go in the body in the psychedelic form and come out as a metabolite. For example, the psychoactive ingredient in marijuana is THC (delta 9 tetrahydrocannabinol). This is oxidised by the body and comes out as many different metabolites. The most prevalent form is Tetrahydrocannabinol-11-carboxylic acid (THC-COOH).

Cannabis is passed from the lungs to the bloodstream, and while the drug is freely floating in the body in sufficient quantity a high is felt. Cannabis is liposoluble, meaning it absorbs into fat cells. The drug is stored in the fat cells indefinitely until the body burns the fat cells for energy. When the cell is burned, the drug is metabolised and released back into the bloodstream. This is why cannabis can be detected in urine for up to 30 days after chronic and frequent usage.

The EWDTS guidelines’ cut off for cannabis in urine on the screen stage is 50 ng/ml, which is a composite of all cannabis metabolite concentrations. If the sample is below this level the test is classed as a NEGATIVE and therefore a PASS result. 

If the sample is over 50 ng/ml it is sent to a laboratory for confirmation analysis. The EWDTS guidelines’ cut off for the confirmation stage in urine is lower at 15 ng/ml because the lab specifically looks for one of the many metabolites – Tetrahydrocannabinol-11-carboxylic acid (THC-COOH). This metabolite can also be referred to as 11-nor-9-Carboxy-THC, also known as 11-nor-9-carboxy-delta-9-tetrahydrocannabinol, 11-nor-9-carboxy-delta-9-THC, 11-COOH-THC, THC-COOH, and THC-11-oic acid. 

  • Any result for Tetrahydrocannabinol-11-carboxylic acid (THC-COOH) <15ng/ml will be reported as NEGATIVE (PASS). 
  • Any result for Tetrahydrocannabinol-11-carboxylic acid (THC-COOH) >15ng/ml will be reported as POSITIVE (FAIL) unless overturned by a Medical Review Officer (a trained individual, usually a doctor).

At this point, you can then act upon this result (e.g., disciplinary) as it is now a legally defensible and a QUANTIFIABLE result unlike the screen QUALIFIABLE result of just “Non-Negative”.

The Limitations of Point of Care Devices

  1. The Point of Care Drug Test provides only a qualitative, preliminary analytical result. A bit like a “Lateral Flow COVID test”. A secondary analytical method must be used to obtain a confirmed result (a bit like a “PCR COVID test”). Laboratory analysis via GC/MS or LC/MS etc are the preferred confirmatory methods. These should be done by a UKAS ISO17025 accredited laboratory.
  2. There is a possibility that technical or procedural errors, as well as other interfering substances in the urine/oral fluid (“saliva”) specimen may cause erroneous results.
  3. Adulterants, such as bleach and/or alum, in urine specimens may produce erroneous results regardless of the analytical method used. If adulteration is suspected, the test should be repeated with another urine specimen and a new test device.
  4. A “non-negative” result does not indicate intoxication of the donor, the concentration of drug in the sample, or the route of drug administration.
  5. A Negative result may not necessarily indicate a drug-free sample. Negative results can be obtained when a drug is present but below the cut-off level of the test.
  6. Tests do not always distinguish between drugs of abuse and certain medications – and further analysis may be required.
  7. A “non-negative” test result may be obtained from certain foods or food supplements.

False “Positives” and False “Negatives”

During the screening stage of the drug test, the result is never 100% accurate. There is a degree of in-accuracy based around “specificity”, “sensitivity” and “accuracy”. 

Point of Care test kits can often be > 99% accurate (this can differ depending on the drug types tested for). You will therefore experience a very small amount of “false positives” and “false negatives”. You will never know about “false negatives” as the donor is unlikely to argue that they should not have passed their drug test (although this does occur where we are testing to confirm and expecting to see if a drug is actually in their system).

A false positive is defined as a drug free sample falsely being reported as showing positive for drugs and or metabolites. This can occur for several reasons including: improper procedure, mixing up samples, and passive inhalation. But the most common cause of drug testing false positives are cross reactants. A cross reactant is a substance which because of its similar chemical structure to a drug or its metabolite can cause a false positive screen result.

The following substances can cause cross reactivity on a “screen test” but are highly unlikely to be mistaken on a “laboratory confirmation test”:


Ibuprofen is a common pain reliever and anti-inflammatory which even in low doses used to cause a false positive for marijuana/cannabis on a screen test. The screen test has been changed to use a different enzyme to eliminate these drug test false positives. But recent evidence suggests that Ibuprofen taken in very high doses, along with other anti-inflammatories such as Naproxen could still interfere with a screen test result.

Decongestants and Cold Remedies

Phenylpropanolamine and ephedrine are both substances found in many over-the-counter cold remedies. They can result in a drug test false positive for amphetamines on a screen test. Antitussives, to suppress coughs, such as dextromethorphan and pyrilamine may cause a drug test false positive for opiates.


Aside from when this class of drugs is specifically tested for, some of them including amitriptyline can test positive for opiates for up to three days after use. Even quinine in tonic water can very occasionally also cause a positive result for opiates. The antidepressant Wellbutrin, and tricyclic antidepressants can trigger false-positive results on tests for amphetamines


Certain newly developed antibiotics including amoxicillin and ampicillin have been reported to cause false positives for cocaine. However, false positives for cocaine are highly infrequent.


This treatment developed for use by patients with AIDS will cause a false positive for anabolic steroid use. Medication for the treatment of HIV/AIDS (Sustiva) can also cause a false positive for cannabis.


Diazepam may cause a false positive for PCP.


A small fraction of the population excretes large amounts of certain enzymes in their urine which may produce a positive drug test. The enzymes in question are endogenous lysozyme and malate dehydrogenate, which according to research may run as high as 10% of false positive samples.


Tablets (venlafaxine hydrochloride) a treatment for depressive, anxiety and social disorder have shown to cause false positive urine results for Phencyclidine (PCP).


Tramadol can give a false positive for Methadone. This is because they are both “synthetic” opiates (otherwise known as opioids).

NOTE: It is recommended that you refer to the specific POC testing device “Product Insert” that you are utilising for your testing program. This will contain further information regarding known cross reactivity for that device.

In summary

  • In any drug screening process, you are likely to encounter a very small degree of false positives and false negatives. You are unlikely to know about false negatives. 
  • All positive (“non-negative”) drug screen results should be further analysed by confirmatory methods at a UKAS 17025 accredited laboratory.
  • It is the confirmation results that are definitive.
  • False positives are mainly caused by cross-reactivity.
  • Occasionally false positives can be caused by operator error.
  • Nothing should be inferred by a false positive screen result. Therefore, we recommend calling it a “non-negative” or “presumptive-positive” screen result.

Choosing the right specialist provider / partner is paramount. It can ensure a legally defensible, robust and consistent service using high quality “fit for purpose” products that can help protect all stakeholders – including Employers and Employees.

For further information about this subject or any other subject regarding Drugs and Alcohol in the workplace, please contact the author:

Matt Taylor


Innovative Testing Solutions Ltd

T: +44 (0)1782 358058
M: +44 (0)7821 116117

Matt is Managing Director of Innovative Testing Solutions, a quality led business delivering innovative, evidence based, high quality diagnostic products to customers in the UK, Ireland and further afield. Matt has been described as a “focussed, dynamic and highly motivated entrepreneurial Director” with a deep industry knowledge and over 18 years of “hands-on” experience within the Drugs and Alcohol Policy, Training and Testing sector. Matt has specialist knowledge within Policy, Point of Care testing and Sample Collection – including application of those skills during the last 18-24 months to COVID testing (PCR & LFD).

OH Today Summer 2022


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