Study signals biomarker hope for monitoring COPD

The biomarkers desmosines and C-reactive protein (CRP) could be used to assess disease severity in chronic obstructive pulmonary disease (COPD), show the results of a Swedish study.

Researchers found that both biomarkers were significantly and inversely associated with several measures of lung function in COPD patients, but not in those without COPD.

Gunnar Engström (Lund University, Malmö, Sweden) and colleagues believe their findings could lead to ways of monitoring lung function decline without the need for repeated lung physiology tests.

"There is a great need for biomarkers that could be used as sensitive measures of the disease activity and assist as predictors of lung function decline," they comment.

The study included 357 individuals enrolled in the Swedish Twin Registry. The participants' lung function was tested by measuring forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), residual volume/total lung capacity (RV/TLC), and carbon monoxide diffusing capacity (D_LCO). Blood samples were also taken to test levels of 10 biomarkers, including CRP, desmosine, clara cell protein 16 (CC16), matrix metalloproteinase 9 (MMP-9), and plasminogen activator inhibitor 1 (PAI-1), which have been proposed as markers for COPD.

Using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification, 67% of individuals in the study had normal lung function and 33% had COPD, of which 60% were classified as GOLD I, 36% as GOLD II, and 4% as GOLD III.

Overall, desmosines, CC16, and CRP inversely correlated with FEV₁ and DLXO, RV/TLC, and FVC and D_LCO, respectively.

However, when the authors looked only at patients with COPD, they found significant inverse relationships between desmosine levels and FEV₁, FVC, and D_LCO. In non-COPD individuals, only the relationship between desmosines and D_LCO was significant.

Likewise, CRP significantly and inversely correlated with all measures of lung function, but only in COPD patients.

Aside from a relationship between MMP-9 and RV/TLC, these were the only significant correlations between biomarkers and lung function in COPD patients.

The authors also found that PAI-1 activity was significantly associated with lung function in those without COPD, but not in COPD patients, suggesting it may indicate early declines in lung function.

CRP is a non-specific marker of systemic inflammation, and has been associated with COPD on many occasions. By contrast, the authors believe that this is one of the only studies assessing the relationship between desmosines ‑ which are released during elastin degradation ‑ and lung function.

Reporting in Respiratory Medicine, Engström and colleagues say that these two compounds could now become useful markers of disease severity in COPD.

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