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Dr Simon Davis asks if you should you consider adding point-of-collection testing devices to your occupational health testing programme?

Occupational health drug testing programmes are an essential part of modern workplaces, protecting the public and workers from the potentially lethal effects of drug and alcohol abuse.
Although the need for testing programmes is largely undisputed, the methods used to test workers are still evolving.

Traditionally, drug testing programmes required the collection of samples, such as urine, which are sent to a laboratory for analysis. Once the results are reported, appropriate actions are taken if any evidence of drug and alcohol abuse is identified.

The benefit of this approach is that the analysis can be performed on highly accurate instruments called Mass Spectrometers. These devices can detect the chemical signature of drugs of abuse down to a few parts per trillion in urine. Also, the chemical fingerprint is highly specific making it unlikely an innocent compound can be misidentified as an illicit drug. This means there is a high degree of confidence in this type of testing programme.

Employees can be confident they will not be falsely accused of drug abuse and employers can be confident that results will stand up to legal scrutiny if disciplinary actions are appealed in court.

Despite the benefits, there are two potential problems with the traditional approach. Firstly cost, laboratory analysis is expensive. This may limit the number and frequency of workers that can be
tested. It may also limit the number of drugs that the programme can test for. Secondly, and of greater importance, is the lag time between sample collection and reporting of the results.

Even when sample analysis is expedited, it takes at least 24 hours before the results are known. Normally, it is two to three days after sample collection before results are reported. During this period, it is possible that a worker who has provided a positive urine sample could continue to drive a train or operate safety-critical equipment until the laboratory analysis has been completed. For this reason, there is a strong argument to use an onsite testing method that would provide results in minutes rather than days.

Instant onsite testing has always been the holy grail of occupational health drug and alcohol programmes. However, this has been difficult to achieve with the accuracy and confidence of the back-to-laboratory approach. To enable onsite testing, there have been many attempts to take the laboratory to the test site. This normally involves creating a testing facility in the back of a van or lorry.

However, the very specific requirements of high voltages, stable temperatures, low dust, and vibration environments have meant these attempts have all failed. It is also questionable whether the high accuracy and cost of mass spectrometry are necessary for an initial onsite screening. Instead, PoCTs provide a quick and economic method to screen workforces on-site for abnormal results. Such results are reported as ‘non-negatives’. Anyone with a nonnegative result can be suspended whilst a second sample is sent to a laboratory for confirmation testing.

This approach is appealing for two reasons. Firstly, anyone who may be abusing drugs and alcohol is immediately stopped from carrying out any safety-critical activities. This removes any immediate risk to co-workers and the public. A suspension is a neutral act under British law, so if the confirmation testing is negative, the worker can be reinstated without any further consequences for the worker or the employer. Secondly, this screening method makes it economically feasible for employers to screen more workers more often. This increases the accuracy of the testing programme and the probability of testing someone in the detection window after they have taken drugs or alcohol.

Rapid low-cost drug testing devices have been available for some time but have met with distrust from workers and unions alike. This has been down to two factors, the lack of familiarity with the technique and concerns about its accuracy.

Over the past few years, we have all become painfully familiar with rapid point of-collection testing devices (PoCTs). These tests are commonly referred to as lateral flow devices and use an immunoassay technique to identify the presence or absence of a protein in the coronavirus. We have all swabbed our noses and throats and sat down to watch with dread for the appearance of the little blue line.

Rapid drug testing devices are available that function in the same way as lateral flow devices. The presence or absence of the drug in the sample is, again, determined by an immunoassay technique in the same manner as Covid-19 lateral flow devices. The results are then displayed by the presence or absence of a line, again in the same manner as a lateral flow test.

Although we are now familiar with PoCT devices, the concerns over accuracy remain. This concern has some basis in fact. Back in 2006/7, the EU published two major studies on the accuracy and use of PoCT devices for the detection of drugs of abuse. These studies, ROSITA-ROSITA 2 and DRUID found that many of the commercially available devices had accuracies of less than 70 per cent. The conclusion of the reports was that poor accuracy made these devices unsuitable for police use or uses that required the results to be legally defensible. These results were disappointing. However, PoCT devices have undergone significant development over the past 15 years. Improvements in immunoassay and wick technology have resulted in game-changing increases in PoCT accuracy.

We have been monitoring the performance of PoCT devices at Imperial College over this period. We are now finding the accuracy of a range of PoCT devices is in excess of 92 per cent when identifying true positives (sensitivity) and 97 per cent when identifying true negatives (specificity). The EU studies stated that PoCT devices could be used if their accuracy exceeded 85 per cent.

The availability of accurate low-cost PoCT devices now makes it possible to design an occupational health testing programme that includes onsite screening. Even though the accuracy of PoCTs is greatly improved, it is still not as accurate as back-to-laboratory testing. Therefore, non-negative results would still require laboratory confirmation.

The combined forces of the Covid-19 pandemic experience and the improvements in device accuracy now mean that all occupational health drug testing programmes should seriously consider
the use of PoCTs as an onsite screening tool. They reduce costs, remove the risk of laboratory reporting delays and raise the possibility of increasing the number of tests performed.

For more information about using PoCTS in your drug testing regime, get in touch via the contact information below.

Dr Simon Davis, BSc, PhD is a Senior Research Scientist at Imperial College London and scientific advisor to Express Medicals.

Tel: 020 7500 6900
Email: workhealth@expressmedicals.co.uk
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