Diseases such as lung and esophageal cancer, kidney failure, asthma and diabetes can all be detected in the breath of people, even before their external symptoms begin to show. This has been the focus of studies looking into whether dogs could be used to sniff out certain cancers, but researchers from the University of Adelaide are looking instead at using light.

In what the scientists are calling an “optical dog’s nose,” the new instrument in development uses a special laser to determine the molecular content of a sample of breath. By measuring the different levels of products of metabolism, or metabolites, and other chemicals generated by different diseases, they hope to be able to produce a non-invasive breath test for a wide variety of illnesses.

“Rather than sniffing out a variety of smells as a dog would, the laser system uses light to 'sense' the range of molecules that are present in the sample,” says Dr. James Anstie from the University's Institute for Photonics and Advanced Sensing. “Those molecules are by-products of metabolic processes in the body and their levels change when things go wrong.”

The technology works by using what’s called "optical spectroscopy." This sends up to a million different light frequencies through a sample of the person’s breath, and as different molecules absorb light at different frequencies, they produce a unique molecular fingerprint. This can then be used to determine the presence of disease.

The researchers detail in Optics Express how using optical spectroscopy allows them to be able to detect these different chemical signatures with a high degree of accuracy and speed. The instrument also lets the scientists test for a wide range of diseases all at the same time. They hope that they will have a working prototype in two to three years, and that this will then lead to the real product coming to clinics in five years' time.

“We now have a robust system to be able to detect the presence and concentrations of molecules in a sample,” says Dr. Anstie. “The next step is to work out how to accurately sample and interpret the levels which will naturally vary from person to person.”