Future drug tests could be as simple as taking a finger print sample thanks to a study led by the University of Surrey.

A team of researchers used mass spectrometry to look at the fingerprints of patients undergoing drug treatment. They tested prints against saliva samples to see if the tests had the same results.

"When someone has taken cocaine, they excrete traces of benzoylecgonine and methylecgonine as they metabolise the drug, and these chemical indicators are present in fingerprint residue," said lead author Melanie Bailey from the University of Surrey.  "For our part of the investigations, we sprayed a beam of solvent onto the fingerprint slide (a technique known as Desorption Electrospray Ionisation, or DESI) to determine if these substances were present. DESI has been used for a number of forensic applications, but no other studies have shown it to demonstrate drug use."

The easy new test could be used for applications such as "probation services, prisons, courts and other law enforcement agencies." It is a significant improvement to traditional methods of testing that require collection of bodily fluids because there are no privacy issues and infection risks are not a concern.

"The beauty of this method is that, not only is it non-invasive and more hygienic than testing blood or saliva, it can't be faked," Bailey said. "By the very nature of the test, the identity of the subject is captured within the fingerprint ridge detail itself."

The technology is also portable and could eliminate the need for off-site testing.

"We are only bound by the size of the current technology. Companies are already working on [miniaturized] mass spectrometers, and in the future portable fingerprint drugs tests could be deployed. This will help to protect the public and indeed provide a much safer test for drug users," Bailey said.The findings were published in a recent edition of the Royal Society of Chemistry.