The lung protein that tells all

Researchers found that serum levels of surfactant protein D (SP-D), a protein that protects the lungs against pathogens and regulates inflammation, increased when patients with chronic obstructive pulmonary disease (COPD) experienced acute exacerbations¹. This supports other studies indicating that the protein could be used to diagnose acute exacerbations of COPD and monitor the progress of the condition.

Chronic obstructive pulmonary disease is a progressive lung disease that makes it hard to breathe. It is often accompanied by an acute worsening of the condition, called an exacerbation. However, there is no validated test to diagnose this acute event. Lung function is generally tested using a spirometer, which involves taking a very deep breath then exhaling forcefully into the device. But spirometry is not recommended in unstable patients. Thus, methods are needed to diagnose exacerbations and monitor their progress.

The researchers compared SP-D serum levels in 28 healthy individuals with those of 28 patients with stable COPD at Al Assad University Hospital in Damascus, Syria, and another 28 patients experiencing an acute exacerbation of the condition.

Serum SP-D levels were significantly increased in all patients with COPD compared to the healthy cohort. They were also significantly higher in the acute compared to the stable COPD patients.

The clear difference in the levels between the two groups of COPD patients indicates that serum SP-D could be used as a biomarker to diagnose exacerbation, the researchers say.

Airway inflammation that occurs during acute exacerbations of COPD is associated with the elevation of a variety of substances in the circulation. However, they are largely synthesized outside the lungs and their relationship with COPD is unclear. SP-D, on the other hand, is produced by lung cells and is one of the few lung-specific proteins that can be tested in the circulation. This makes it a useful biomarker to track the health status of patients with COPD.

The study, published in the Qatar Medical Journal, is the first conducted in Syria on the potential of serum SP-D as a biomarker of COPD exacerbations. The researchers recommend further research to elucidate the precise mechanisms involved in increasing SP-D levels in COPD, which are still unclear. The team hopes to conduct further research to investigate how changes in serum SP-D levels can predict severe exacerbations and how the protein can be used in clinical practice.

1. Zien Alaabden, A., Mohammad, Y. & Fahoum, S. The role of serum surfactant protein D as a biomarker of exacerbation of chronic obstructive pulmonary disease. Qatar Med. J. 2015, 18 (2015). | article