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A new test can identify lung cancer by detecting unique chemicals in the breath of those suffering from it.
The breath test uses a small array, less than an inch square, of 36 spots of chemically sensitive compounds that are designed to change colour when they come into contact with specific chemicals in the breath of patients with lung cancer.
There is evidence that the breath constituents of lung cancer patients are different from those of healthy people. Metabolic changes in lung cancer cells cause changes in the production and processing of volatile organic compounds, which are then breathed out. But no single volatile compound has been found that can be used to diagnose the disease.
A team from the Cleveland Clinic in Ohio used the array of spots to try to establish a pattern of colour changes that characterises lung cancer.
They tested the breath of 122 people with a variety of respiratory diseases, and 21 healthy controls. The group included 49 people with small-cell lung cancer at various stages of development. The research team used the results from 70 per cent of the study participants to develop a predictive model, the accuracy of which was tested on the remaining 30 per cent.
The results showed that the test was able to predict the presence of cancer with â€œmoderateâ€ accuracy. It was right in about three out of four cases.
Other approaches to breath testing had been used, the authors said in the journal Thorax. These included gas chromatography-mass spectrometry, an expensive method requiring a great deal of expertise.
Lung cancer was often detected late, so any simple tests that could detect the disease sooner would be valuable and might lead to better treatments, Dr Peter Mazzone said.
So far, the best results reported come from the use of dogs. A team led by Michael McCulloch, of Pine Street Foundation in California, trained five â€œordinary household dogsâ€ to distinguish by scent the breath of 55 lung cancer and 31 breast cancer patients. In lung cancer patients the diagnostic accuracy was 99 per cent and in breast cancer it was 88 per cent, they reported last year.