what substances can cause a false negative?

Within the construction, railway, aviation, energy, healthcare, and shipping sectors, drug, and alcohol testing is used to ensure that workers can work safely. With regular screening, companies are able to identify possible problems before they affect the health and safety of any employees and the company itself. 


Drug & Alcohol testing for the Construction Industry 


Construction, behind farming, is the 2nd most hazardous industry to work in, due to the exposure and use of heavy machinery, hazardous materials, heavy lifting, and working at heights, However, despite this, no legislation requires mandatory drug and alcohol testing for the construction sector. 

Although Barratt Developments, Britain’s largest housebuilder, introduced randomised drug and alcohol testing in 2018. Realising the importance of screening, as they feared the potential rise in substance abuse, and the potential consequences this could have. 


Drug & Alcohol testing for the Railway Industry 


However, the story is a little different for the railway industry as drug & alcohol testing is mandatory. The railway industry sets the standard for best practice in regard to drug and alcohol testing for its workers. The Transport and Works Act (1992) stated that those who are found to be impaired by drugs or alcohol are guilty of a criminal offence. This is why screening is completed regularly within the industry.  

RISQS standards must be upheld with the rail industry companies across the UK. Acorn is RISQQ accredited to provide medicals for the railway industry, with options for PTS medicals which include drug & alcohol testing. 

Changes to RISQS Guidance


Recent changes to RISQS guidance now mean that drug tests are not required to be sent to the laboratory unless a non-negative result is produced. With ‘point of care’ tests now acceptable, meaning tests can be completed and reach a conclusion at the ‘point of care’.

*Please note that ‘point of care’ is a term used for on-the-spot testing and results, rather than results being sent to another location.


Substances that are tested for 


Alcohol testing is carried out using a breathalyzer machine and will indicate the presence of alcohol. 

However, drug testing is carried out by taking a sample of Urine or taking a mouth swab. The groups of testing for drugs can vary, however, best practice is to normally include 6 to 7 groups, with at least the 4 core groups below being included in tests. 

  • Cannabis 
  • Cocaine 
  • Amphetamine 
  • Opiates 


Additional drug groups can include Methadone, Methamphetamine Benzodiazepines and Propoxyphene, and MDMA (Ecstasy).


 Can some substances cause a false negative?


Cut-off levels for urine drug tests mean that only when a certain level of a substance is detected, a positive result will occur. These cut-off levels help to prevent false positives, and also reduce the chance of testing positive after a passing exposure. 

Guidelines: http://www.ewdts.org/ewdts-guidelines.html

Before taking any drug tests, any prescribed medication must be declared and proved i.e. with a prescription. This declaration could help to explain should a positive result occur, and that levels are in line with ‘therapeutic’ usage. 


Drug & Alcohol testing at Acorn Occupation Health 


Drug screening procedures may be performed using either mouth swabs or urine samples. These procedures are fully validated and subject to stringent quality control under the ‘chain of custody’. Our Alcohol screening procedure may be performed by using a urine sample or by using one of our Alcometers. 

We have a wide range of medical testing options at Acorn means we can carry out desired assessments on employees. Our PTS Medicals includes 3 variations: 


Drug and Alcohol test sent to the laboratory: £60 + vat

Drug and Alcohol test point of care(not to the laboratory): £50 + vat

Single PTS Medical: £85 + vat

Full PTS Medial with Drug and Alcohol: £145 – £155 + vat


Acorn Occupational Health can assist with policy writing and play a vital role in supporting managers and human resource personnel to effectively manage drug and alcohol abuse. Our experienced Medical Technicians/Occupational Health Nurses aim to deliver a discrete, confidential, and cost-effective service designed to meet the needs of your business.


Contact Us 


For more information on our drug and alcohol testing, explore our medical services, or get in touch. Call us on 01260 277797 or email us at website@acornoh.co.uk

Want to know more about the Occupational Health services we provide at Acorn, and how they could benefit your business and your employees? Please get in touch.