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Endothelial Microparticles (EMPs) in the Blood Useful for Identifying Early Signs of Emphysema

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According to a recent study published in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine, small particles in the blood released by cells lining the lungs may help clinicians diagnose emphysema in its earliest stages. The particles, called endothelial microparticles (EMPs), are shed during disease progression as pulmonary capillaries in the lungs are injured and die.

According to Ronald Crystal, MD, chairman and professor of genetic medicine at Weill Cornell Medical College:

This study confirmed that levels of EMPs are elevated in the blood samples of smokers, consistent with the concept that emphysema is associated, in part, with the death of cells lining the pulmonary capillaries, and suggesting that the early development of emphysema might be monitored with blood tests to measure EMP levels.

Based on the findings of previous studies, which have linked cardiovascular disease with elevated blood levels of EMPs, researchers hypothesized that EMP levels might also be elevated in patients in the early stages of emphysema.

To test this hypothesis, two lung function tests were used: spirometry, which measures the amount and speed at which a patient exhales, and a lung diffusing capacity (DLCO) test, which measures the lung’s ability to transfer carbon monoxide. Patients with early emphysema typically have normal levels of inhalation and exhalation, but exhibit low DLCO.

Researchers evaluated the levels of circulating EMPs in a patient population of 92 subjects divided into three classes: healthy nonsmokers, healthy and symptomatic smokers with normal lung function, and healthy smokers with normal spirometry but low DLCO. Because smoking is known to affect blood vessels in many areas of the body, EMPs were assessed for a specific enzyme that occurs primarily in pulmonary vessels. The findings were then validated in two prospective cohorts.

The investigators found that both symptomatic smokers and healthy smokers with normal spirometry and normal DLCO had mild increases in EMP levels compared to healthy nonsmokers. There was no difference in the levels of EMPs between healthy and symptomatic smokers. However, almost all healthy smokers (95%) with normal spirometry but low DLCO had a significant increase in EMP levels.

Dr Crystal said that the study results suggest that vascular-based contributions to the development of emphysema may contribute to the early development of the disease, a point at which smoking cessation therapy may prevent the irreversible lung destruction that is associated with the development of COPD.

A future blood test to measure EMP levels may offer a safer and inexpensive alternative to the technique currently used to identify early-onset emphysema, high-resolution computed tomography (HRCT),

Study: Circulating Endothelial Microparticles as a Measure of Early Lung Destruction in Cigarette Smokers

Source: American Thoracic Society