A study of the relative performance of market leading urine point of
collection screening devices used to detect drug abuse within occupational
testing programmes
Dr Simon Davis B.Sc. Ph.D. Senior Research Scientist.
Imperial College London.
Correspondence address-simon.davis@imperial.ac.uk
Date of publication: 02 November 2015.
The work contained in this report has been carried out under the instruction of Express Medicals Ltd
(EML). The devices tested in this study have been supplied by EML under request from Imperial
College. All other aspects of the study have been carried out by Imperial College, London and
represent an objective and independent review of the devices supplied.
Point of collection testing (PoCT) devices are commonly used to screen for drug abuse in the
workplace. These devices are cheap and simple to use with the added benefit that screening takes
place at the employee’s workplace. This results in limited disruption to the individual and the
working environment. The devices also provide near instantaneous results, unlike laboratory testing
where the reporting of results commonly take up to five working days following collection of a
sample.
PoCT devices depend upon a biological process known as an immunoassay. If a drug is present in a
sample biological activity creates a coloured band or mark to appear in the indication window of the
device. This is identical to the process used in most common pregnancy testing kits.
Despite the clear benefits of PoCT use, it is important to remember that these devices provide lower
levels of analytical precision when compared to laboratory-based testing programmes. The reduced
precision is likely to manifest itself in a number of false positive and / or false negative results. Due
to the possibility of erroneous results it is important that PoCT devices are used as part of a
screening programme. This means that a positive sample identified by a PoCT device must be
treated as a “presumptive” or unproven result. The presumptive positive samples must be sent for
laboratory confirmation of the results. This has two benefits : (i). Employees are not sanctioned for
drug use when they are innocent. (ii). True positive results (confirmed by subsequent laboratory
analysis) become legally defensible at work tribunals or other forms of judicial review.
Although screening removes issues relating to false positive results (because a presumptive PoCT
screen result will be followed by a laboratory test) it does not remove the risk of false negative
results. This means that an individual could pass a PoCT screen when they are intoxicated or
otherwise impaired through drug use. The only way to avoid the possibility of any false negative
results is to follow every PoCT screen with a laboratory test. It is, therefore, important to consider
whether PoCT screening (without subsequent laboratory testing) is suitable for safety critical
environments where false negative results could cause serious harm.
Despite their widespread application, currently there are no national or international regulatory
bodies controlling the manufacture, use or supply of these devices. This means that any individual
with a rudimentary scientific knowledge can manufacture and sell PoCT devices without any form of
quality control.
The problems this can create were highlighted in a recent study by Imperial College and Express
Medicals Limited (EML). This study looked at the quality and analytical performance of cheap PoCT
devices imported from China into the European market. The ability of these devices to detect up to
11 different drugs were tested. The study found that on average the imported PoCTs could only
identify 32% of samples which contained drugs on the devices detection list. This would mean that
68% of drug abusers would pass any screening programme which used these devices.
It is, therefore, clear that the selection of high quality PoCT devices is essential to ensure the success
of any screening programme. In the absence of national or international regulatory bodies it is
necessary to carry out independent performance verification, as has been done here.
Due to these concerns, EML instructed Imperial College to carry out performance verification studies
on high quality urine PoCTs manufactured by three different companies. The screening devices
studied were:
All.Diag DrugCheck 11 urine PoCT (France)
Discover multi-panel urine PoCT (USA)
Medax KC 602A urine PoCT (Germany)
The results of the study showed that the devices performed well (Figure 1 and Table 1) with all
PoCTs exceeding 96% detection rates. However, All.Diag detected 100% of all samples containing the
drugs listed on its detection panel. To test the All.Daig capabilities further the concentration of the
drugs within the sample were reduced to 10% below their reported detection levels and the
experiment repeated. Once again the All.Diag devices correctly identified 100% of the positive
samples.
The performance of similar PoCT devices is variable but typically display an accuracy of 94%
(Lewandrowski et. al. 2008; Luzzi et. al. 2004; Melanson et. al. 2010; Reisfeld et. al. 2009). This
shows that All.Diag devices significantly outperform similar market leading products. As a result
All.Diag PoCTs can be used with confidence in any occupational screening programmes employing
urine as the testing medium to detect the compounds listed on the devices’ drug panel.
Table 1.The percentage detection accuracy of three market leading urine PoCT devices. All.Diag presented the highest level
of performance with 100% detection rates.
Compound
Amphetamine
Secobarbital
Oxazepam
Buprenophrine
Benzoylecgonine
Methadone
D-Methamphetamine
D-Methylenedioxymethamphetamine
Morphine
Nortriptyline
11-nor-delta9-THC-9-COOH
Cocaine
Benzodiazepines
Opiates
All.Diag
Detection
rates (%)
100
100
100
100
100
100
100
100
100
100
100
N/A
N/A
N/A
Discover
multi-panel
Detection
rates (%)
100
N/A
N/A
100
N/A
100
N/A
N/A
N/A
N/A
90
100
100
100
Medax
Detection
rates (%)
100
N/A
N/A
N/A
N/A
100
N/A
N/A
N/A
N/A
90
100
100
90
MDMA
Propoxyphene
N/A
N/A
100
100
N/A
N/A
Figure1. The percentage detection accuracy of three market leading urine PoCT devices. All.Diag presented the highest
level of performance with 100% detection rates.
Analytical accuracy of PoCT devices by
manufacturer (%)
100.0
98.9
96.7
All.Diag (Urine)
Discover multi-panel (Urine)
Medax (Urine)
Based on the results of this study, it is clear that each of the three devices performed well. However,
the All.Diag PoCTs showed the highest analytical accuracies of the three devices tested. As such it is
the recommendation of this report that All.Diag oral fluid PoCTs should be preferentially used in any
occupational screening programmes employing urine as the testing medium and wishing to detect
the compounds listed on the devices’ drug panel.
References
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