US scientists have developed and tested a prototype breath test to detect lung cancer.

The results of the test is published in the international journal of respiratory medicine Thorax.

In tests, the colour testing device, which is about the size of a coin and is not expensive, had a 75 per cent success rate in detecting people with cancer.

It can also detect people with early stages of lung cancer.

However, in testing the device also showed false positives - it picked out people without lung cancer.

Using a technique called a "colorimetric sensor array", the test picks up the chemical fingerprint of the breath of people with lung cancer.

Lung cancer tumours, like other cancers, produce volatile organic compounds (VOCs) that are different to normal cells. And because the tumours are in the lungs, the breath is likely to contain signs of these abnormal compounds. This means the potential for a lung cancer "fingerprint" in the breath is a viable method for detection.

Dogs are also able to detect VOCs and differentiate between people with lung cancer and healthy people.

The prototype device in this instance was developed by Dr Peter Mazzone of the The Cleveland Clinic in Ohio in collaboration with the private company ChemSensing of Champaign, Illinois. The private company customizes Metalloporphyrins, a family of chemically reactive dyes that are sensitive to VOCs.

The idea was to develop an inexpensive, portable device. The only other equipment available are mass spectrometers or gas chromatographs, which are expensive and need an expert to analyse the results.

The device looks like a small 2 cm square transparent key fob with a 6 by 6 pattern of coloured dots visible through the plastic. The pattern of the dots changes depending on the gas makeup of the breath.

In the tests the scientists invited 143 patients to breathe into the device for 12 minutes. Some of the patients had lung cancer at various stages, some of them had other forms of respiratory illnesses such as emphysema and the rest were healthy.

The device spotted 73 per cent of the lung cancer patients and cleared 72 per cent of the non-lung cancer patients.

Dr Mazzone and his colleagues hope that this test will pave the way for the development of inexpensive, non-invasive screening tools for lung cancer detection.

Lung cancer is not easy to detect in its early stages, when it is still treatable, and many patients don't notice the signs until symptoms are well developed and the cancer has spread.

According to the US National Cancer Institute, cancer is the second most common cancer and the most common cause of cancer-related deaths in the US. Every year over 200,000 new cases are diagnosed, and over 160,000 deaths occur due to the disease.

The World Health Organization (WHO) puts the global annual death rate from lung cancer at 1.3 million.

Click here for Lung Cancer Online (US).

Click here for Thorax journal.

Written by: Catharine Paddock
Writer: Medical News Today