Blood Test Catches Secret Smokers

MONDAY Oct. 22, 2007 -- If you're sneaking smokes when no one's looking, beware: One lung doctor says a common device can determine whether someone is a smoker.

The blood carbon monoxide detector could be used to ferret out people who hide a cigarette habit, said pulmonologist Dr. Sridhar Reddy. It could also help show patients what smoking is doing to their bodies, he added.

"It starts a conversation to make people more and more aware of what smoking can do to them and to give them more information about why they should quit, instead of a boring sermon every time," said Reddy, who works in St. Clair, Mich.

There are already ways to detect whether someone is a smoker, according to Reddy. Doctors can test a person's breath, blood or saliva.

But none of the methods is very convenient, Reddy said, so he decided to take a look at another device.

Anyone who has been in a hospital recently is probably familiar with the pulse oximeter, a device that's placed over the fingertip and measures oxygen levels in the blood by passing light waves into the skin.

Reddy tested an oximeter that also measures carbon monoxide levels in the blood. It's typically used on firefighters and others who have been exposed to smoke.

With the help of his 16-year-old son, Ashray, who assisted as part of a science project, Reddy tested the device on 476 patients to see how well it did at picking up smokers, who develop high levels of carbon monoxide in their blood.

The device, which Reddy said costs $4,000-$5,000, measures the level of carbon monoxide in hemoglobin. It accurately spotted up 95 percent of all smokers when Reddy looked only at those who had a 6 percent or higher level of carbon monoxide.

The device doesn't detect every smoker, nor is it perfect when it does suggest that someone smokes. Still, Reddy said the device can be calibrated to detect light or heavy smokers.

In his office, he sometimes sets the device to sound an alarm if the carbon monoxide level is higher than 10 percent, meaning that only the heaviest smokers should set it off. Patients wonder why the alarm goes off, and "we can tell them that 10 percent of their blood is poisoned with carbon monoxide. That gets them in a conversation about preventing lung disease even if they don't have it," he said.

Dr. Joseph DiFranza, a professor of family medicine at the University of Massachusetts, Worcester, who's familiar with Reddy's research, said the device could have potential as a smoker-detector, but "I would not recommend that doctors embrace it until it has been demonstrated to be effective in a randomized controlled trial."

Joel Killen of the Stanford Prevention Research Center said the study is interesting, but he added that another device, called a "smokerlyzer," also measures carbon monoxide in the breath and is "non-invasive, easy and inexpensive."

Reddy was slated to discuss the device Monday at the annual international scientific assembly of the American College of Chest Physicians in Chicago.

Also scheduled for the meeting was a study by researchers at the North Shore-LIJ Health System in Great Neck, N.Y., who report that smokers have different motivations for quitting depending in their age. According to their study, people over 65 are more influenced by their doctors and by stress from a health problem, while young people are influenced by the cost of cigarettes and a perception that smoking makes them stink.

Another smoking study scheduled for meeting, this time by a team at North Shore Medical Center in Salem, Mass., found that hypnosis was a better smoking-cessation technique than either nicotine replacement therapy or quitting "cold turkey."

Posted: October 2007


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