In the March 11 online edition of the American Journal of Respiratory and Critical Care Medicine, the researchers say that because most cases of emphysema are caused by smoking, the test they are developing can warn smokers about impending development of the untreatable disease.

Crystal and his colleagues reasoned that as capillaries surrounding the air sacs are  injured, the debris would likely be carried out by the blood supply and could potentially be quantified as a disease biomarker. So they began to look for evidence of what they called endothelial microparticles (EMP).

"Our blood vessels are always being replenished, so we all have some level of EMPs in our blood," he says in the press release. "What we are looking for are elevated levels of EMPs. For smokers, this is the equivalent of a smoke detector sounding its alarm; elevated levels of EMPs suggest their air sacs are being injured and it is time to act."

To do this, the researchers enrolled three groups of people—healthy nonsmokers, healthy smokers, and smokers with early evidence of lung destruction. Study participants had their medical histories taken, and to gauge lung function in these participants, all underwent two pulmonary function tests. One is spirometry, which measures the volume and speed of air as it is inhaled and exhaled from the lungs. The other, known as DLCO, is the only lung function test available today that can detect emphysema in patients. It uses a machine that measures the ability of gases to diffuse across the alveolar-capillary membrane.

The researchers found a 95 percent positive correlation between elevated EMPs in the blood and an abnormal DLCO test result, meaning that it detected nearly all verified cases of early emphysema in participants.

Two other independent groups of participants were then given the same group of tests—spirometry, DLCO and the EMP blood test—and a positive EMP finding correlated with an abnormal DLCO 95 percent of the time. Differences in the spirometry findings had no bearing on results of DLCO or EMP.

DLCO, which must be administered by a pulmonologist, is most often used to confirm a suspicion of emphysema, Crystal says. By contrast, the EMP blood test is designed to be a simple, low-cost screening tool that can pick up development of emphysema in individuals who show no signs of the disorder.

"We need a blood test that can be administered to the 20 percent of American adults who smoke as well as nonsmokers exposed to secondhand smoke—all who may not understand their risk of developing this progressive lung disease," says Dr. Crystal.

The researchers are conducting further studies of the EMP test in larger groups of participants in order to validate these initial findings.

The study was funded by grants from the National Institutes of Health.