Simple test reveals smokers who are less than honest

Smokers who lie about their habit to their doctors could in future be caught out by a simple blood test.

A simple device for detecting carbon monoxide in the blood may enable doctors to receive an honest answer from patients who smoke.

The U.S. researchers have used a device, called a pulse cooximeter, which is commonly used to test for carbon monoxide levels in firefighters.

The device can also detect carbon monoxide levels in people who smoke, and may offer doctors a powerful tool in educating their patients about the effects of smoking.

Dr. Sridhar Reddy, a lung specialist in St. Clair, Michigan, presented the study at a scientific meeting of the American College of Chest Physicians in Chicago, along with his 16-year-old son Ashray.

Dr. Reddy says together they were just trying to solve the problem of screening people for smoking.

Dr. Reddy who encouraged Ashray to take on the study as a school science project, says smokers never volunteer the information that they smoke and when asked directly they often lie.

Dr. Reddy was searching for a quick, convenient method to detect whether a person smokes as current tests involve breath, blood or saliva samples and the methods are inconvenient.

The pulse cooximeter simply involves placing a clip-like device on a finger tip which then reads percentages of poisoned blood through a light that is shined through the finger nail.

Ashray was eager to discover how much carboxyhaemoglobin (blood poisoned by carbon monoxide) would indicate whether a person is a smoker.

Together with his father he devised a questionnaire to determine patients' smoking habits while, Dr. Reddy recruited 476 patients in his office to take the test in order to see how well it did at picking up smokers.

They were able to determine that patients with blood carbon monoxide levels of more than 6 percent were smokers, and Ashray was able confirm this through the patient surveys.

The father and son team believe the device may be a cheap, easy way to help doctors talk to their patients about smoking.

Dr. Reddy says as most patients know what carbon monoxide is they respond strongly when they find it is circulating in their blood.

Dr. Reddy says the device costs $4,000-$5,000 and accurately spotted up 95 percent of all smokers.

Though it does not detect every smoker it can be calibrated to detect light or heavy smokers.

Dr. Reddy now routinely uses the test as part of a patient work-up and instead of asking whether a patient is a smoker, he presents the test results and asks whether the finding could be related to smoking.

He sometimes sets the device to sound an alarm if the carbon monoxide level is higher than 10 percent so only the heaviest smokers set it off.

When patients question why the alarm went off, he tells them that 10 percent of their blood is poisoned with carbon monoxide; that he says gets a conversation going about preventing lung disease.

He hopes this will become a feature of routine screening.

Meanwhile Ashray won a medal at the local science fair.