By the time that smokers develop pulmonary problems following an extended smoking history, the damage is usually permanent. But now doctors may soon have a new tool at their disposal to pick up problems before symptoms appear. And this sort of information will, addiction specialists believe, encourage patients who are at risk to quit before their condition becomes clinically apparent.
The new test, which has been developed by Weill Cornell Medical College physician Ronald Crystal and his colleagues and is published in the American Journal of Respiratory and Critical Care Medicine this month, detects blood-borne structures called "endothelial microparticles" - EMPs - which are small membrane-bound particles derived from the cells that line blood vessels. These particles are liberated into the bloodstream when blood vessels are injured, so the researchers wondered whether they might also be predictive of underlying lung injury such as would happen then the airways, and blood vessels supplying them, are injured by chemicals in cigarette smoke.
To find out, they recruited three groups of volunteers: healthy non-smokers, healthy smokers and smokers with early evidence of lung damage. All three groups underwent pulmonary function tests, including gas diffusion tests, to gauge their lung health. The researchers then compared the levels of EMPs in blood samples from each patient with the results of their respiratory tests.
Abnormal lung function, they found, showed a 95% correlation with elevated EMPs, meaning that this measure was capable of picking up nearly all cases of early-emphysema in the study groups. The researchers then verified the results by testing two further independent patient groups, arriving at the same outcome. This means that EMPs can be used as a low-cost and rapid screening tool to pick up development of emphysema amongst individuals even before they have begun to show any signs.
"We need a blood test that can be administered to the 20% of adults who smoke as well as non-smokers exposed to secondhand smoke - all who may not understand their risk of developing this progressive lung disease," says Dr Crystal.
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