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FALSE POSITIVE DRUG TEST

Ever had a false positive drug test? Well, one of our consultant's just had one.

Drug screening results can affect the lives and circumstances of those involved. In recent times drug testing has gone from a non-existent practice to a widespread acceptance within the construction industry. This is due to the rise in use of recreational drugs. Cannabis users comprise the largest number of illicit drug users in the UK; second are amphetamine-type stimulants, followed by opiate and cocaine.

Approximately 3 million continuous drug users in the UK.

Many companies have adopted a zero tolerance to drugs and alcohol approach. Drugs and Alcohol Policies can include site induction drug screening, random testing, toolbox talks and other media pathways. Concentration and co-ordination are crucial when working in the construction environment. Accidents can occur as a result of impairment or intoxication. Accidents have consequences including loss of time, insurance costs, damages and legal costs etc. Indirect costs can include loss of reputation and confidence in an organisation.

35% of employees have noticed their colleagues under the influence of drugs and alcohol.

Drug testing is not about catching the drug users, it’s about putting control measures in place that prevent the introduction of drug users on to a construction site. If an employee comes forward, the Policy should aim to support the affected employees as opposed to punishing them or dismissing them. Nonetheless, possession or dealing in illegal drugs should be referred to the Police.

It is an offence under the Misuse of Drugs Act 1971 for any person knowingly to permit the production, supply or use of controlled substances on their premises except in specified circumstance e.g. prescribed by a doctor.

It is important for organisations initiating a Drugs and Alcohol Policy to understand the knock-on effects from the outcome. A false positive is when a sample is incorrectly recorded as a positive when the sample is negative, research shows that rates can be as high as 10%-15%.

Drugs Side Effects of Drugs Drug

What can cause a False Positive result?

  • ‘Over the counter’ medicines – Ibuprofen/PCP, Diet Pills/Amphetamines.
  • Foods – Poppy Seeds/Opiates, Hemp Oil/Marijuana, Cocas Leaf tea/Cocaine.
  • Prescription Medication – Antidepressants/Amphetamines, Quinine/Opiates, Tramadol/PCP.
  • Human Error – Contamination, Manipulation.

The consequences of a false positive test differ from loss of employment, social stigma, possible legal action, suspension, stress, loss of money etc. Organisations must ensure that their policy and management arrangements are comprehensive and consider the potential for false positive results.

Many organisations offer a single drugs/alcohol test on induction/randomly, if these test positive operatives are asked to leave site. Urine and Saliva drug tests are common practice on construction sites due to their low cost/quantity and fast results. However; inaccuracy, potential for contamination and lack of ability to measure the frequency of use or impairment are disadvantages of these tests. A comprehensive system would highlight potential positives using a quantitative testing such as saliva or urine test. This would then be supported by a test method with higher accuracy and ability to measure frequency and impairment, such as blood and hair testing. This would counteract false positive results and the consequences thereafter.

Urine Sampling

  • Inexpensive
  • Detects recent drug use (previous 4-72 hours)
  • Can target multiple drugs at once
  • Rapid test results
  • Easily manipulated
  • Collection process is not observed
  • Cannot measure the frequency of use or severity of impairment
  • Invasive test

Oral Fluid Testing

  • Inexpensive
  • Detects recent drug use (previous 4-72 hours)
  • Can target multiple drugs at once
  • Rapid test results
  • Sample collected under direct observation
  • Cannot detect drug use beyond 48 hours
  • Cannot measure the frequency of use or severity of impairment
  • Invasive test

Hair Testing

  • 3 months detection period
  • Can indicate the frequency of drug use
  • Can target multiple drugs at once
  • Sample collected under direct observation
  • Accurate
  • Difficult to manipulate results
  • Expensive
  • Extended result time - 5 days+
  • Invasive test
  • Relies on presence of body hair

Blood Testing

  • Can indicate the frequency of drug use
  • Can target multiple drugs at once
  • Sample collected under direct observation
  • Accurate
  • Difficult to manipulate results
  • Expensive
  • Extended result time - 2 days
  • Invasive test
  • Administered by a Health Care professional

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