Over 8,000 people were arrested in England and Wales for driving under the influence of drugs in the year to April 2016. In fact, 60% of all those stopped by police under suspicion of drug-driving test positive for illegal drugs including cocaine.
Yet the devices used to test for drugs at the roadside can give false positive readings, meaning someone could be arrested for drug-driving when they’re innocent. To combat this, my colleagues and I have developed a new portable system based on a technique called “mass spectrometry” that is much more reliable.
Current roadside testing for drugs is typically carried out by asking a driver to give a sample of saliva on a stick that looks very much like a pregnancy test. Testing for drugs is then carried out using something called an antibody assay.
The antibody molecule “recognises” a particular drug and binds to it, so that the device gives a positive signal if a drug is present. The problem is that in about 5% of cases, these devices give false positive results, because the antibody can bind to substances that are not the drug of abuse.
My colleagues and I have been developing new mass spectrometry approaches for drug detection in body fluids, through a collaboration with the Surrey and Borders NHS Foundation Trust and Advion Limited. Mass spectrometry is a technique that allows us to identify a molecule based on the ratio between its mass and its electrical charge. It is normally used to confirm the presence of drugs of abuse following a positive test at the roadside but has until now been restricted to the lab.
But developments in miniature portable mass spectrometers are gaining pace. In our recent work, published in Analytical Methods, we have demonstrated that you can use a new portable mass spectrometry system to test for cocaine in saliva. Not only is it small enough to be used at the roadside, but it is also about one tenth of the price of the lab-based systems that are used for confirmation testing.