Simple blood test detects early emphysema in smokers before symptoms appear

During a regular annual physical exam, blood is usually drawn to check the health of a person's heart, kidneys and liver. Now, researchers at NewYork-Presbyterian Hospital/Weill Cornell Medical Center say a blood test that detects the early development of emphysema - well before symptoms occur - may someday also be offered.

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 - which is currently a major cause of disability and death in the U.S.

Not all smokers develop emphysema, but those who find out they are at risk will be motivated to quit to halt progression of the disease, says the study's lead investigator, Dr. Ronald G. Crystal, chairman and professor of genetic medicine and the Bruce Webster Professor of Internal Medicine at Weill Cornell Medical College and chief of the Division of Pulmonary and Critical Care Medicine at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.

"We know, from other studies, that smokers who learn from objective evidence that their health is in danger are much more likely to quit," he says. "That is the only thing that will help them avoid this deadly disorder."

Emphysema and chronic bronchitis are the twin disorders that make up chronic obstructive pulmonary disease (COPD), which is now the fourth leading cause of death in Americans. Given the aging population, COPD is soon expected to move up to third in mortality prevalence, Dr. Crystal says.

The new test measures particles that are shed by tiny blood vessels known as capillaries that surround air sacs (alveoli) in lungs. These particles are debris shed by ongoing injury to the air sacs - damage that eventually results in devastation of the sacs and the "Swiss cheese" appearance of the lungs. The alveoli are where critical gas exchanges occur: blood in the capillaries brings carbon dioxide from the rest of the body for release into the air sacs, and the oxygen in the sacs (taken in from breathing) is taken up by the blood and transported to the rest of the body.

As the sacs are destroyed, people develop shortness of breath because they cannot take in enough oxygen to feed the body and eventually cannot remove carbon dioxide from the blood.

Dr. Crystal and his colleagues reasoned that as capillaries surrounding the air sacs are being injured, the debris would 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. "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."