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.