A sensor made with gold nanoparticles can detect lung cancer in a patient's breath and may offer a diagnosis before tumors show up on an x-ray, Israeli scientists said on Sunday.

The device, which the developers say would be cheap enough for everyday use by family doctors, detected lung cancer with 86 percent accuracy and may offer a way to screen for a disease not usually diagnosed until it has spread and is no longer curable.

It uses sensors based on gold nanoparticles to detect specific compounds -- volatile organic compounds (VOC) -- that lung cancer patients have in high levels in exhaled breath.

Breath testing is already recognized as a way of linking specific VOCs in exhaled breath to a certain medical conditions. In 2006, researchers found dogs could be trained to smell cancer on the breath of patients with 99 percent accuracy.

Hossam Haick, one of the scientists working on the sensor, said he hoped it could soon allow doctors to have a simple test at hand to screen people during routine appointments.

Conventional diagnostic methods for lung cancer are unsuitable for widespread screening because they are expensive and occasionally miss tumors, Haick and colleagues wrote in Nature Nanotechnology.

This device is not at all expensive. The whole idea in this development was to devise something very sensitive, and very cheap and very portable, Haick, of the Technion-Israel Institute of Technology in Haifa, told Reuters.

Lung cancer kills 1.3 million people a year and is the leading cause of cancer death across the world. Only 15 percent of patients live more than 5 years, in part because the disease is usually diagnosed so late.

The device developed by Haick and his colleagues is a nine-sensor array consisting of gold nanoparticles combined with different organic groups that respond to various VOCs released by lung tumors.

They tested 56 healthy people and 40 patients who had been diagnosed with lung cancer using conventional methods.

They found the sensor could distinguish the breath of lung cancer patients from the of the control group with more than 86 percent accuracy.

Haick said the patented device needed to be more rigorously tested and obtain approval from drug licensing authorities before it could go into production.

I would say that could take three to five years, he said.

Various other methods exist to measure VOCs, including a breath test using color spots, but existing techniques are often expensive, slow and sometimes require the breath to be concentrated or dehumidified first.

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