Surrogate marker identified for airway obstruction and asthma control

By Lucy Piper, Senior medwireNews Reporter

Researchers have identified a potential biomarker for airway obstruction in patients with asthma that not only reflects airflow limitation but also asthma control.

They found that patients with asthma had significantly higher plasma levels of N-terminal connective tissue growth factor (CTGF) than individuals without the respiratory disorder.

Levels of CTGF were, on average, 1389 pmol/L in 67 patients with stable asthma compared with 1135 pmol/L in 81 healthy volunteers, reflecting a significant difference.

There was also a significant difference in CTGF levels between the 34 asthma patients with a percentage of predicted forced expiratory volume in 1 second (FEV₁) below 80% and the 33 patients with a percentage of predicted FEV₁ above 80%, at 1578 pmol/L versus 1198 pmol/L.

Tomoyuki Fujisawa (Hamamatsu University School of Medicine, Japan) and colleagues report in Annals of Allergy and Asthma Immunology that N-terminal CTGF levels correlated negatively and significantly with parameters associated with the degree of airway obstruction.

These included forced vital capacity (FVC), FEV₁, percentage of predicted FEV₁, the ratio of FEV₁ to FVC, forced expiratory flow at 50% of the FVC (FEF_50%), percentage predicted FEF_50%, FEF_75% and percentage of predicted FEF_75%.

The researchers suggest that CTGF may play a role in the development of airway remodelling and airflow limitation in the asthmatic airway by a process known as subepithelial fibrosis.

“Given that CTGF may play an important role in the development of airway remodelling and chronic airway obstruction, it is reasonable that CTGF levels are related not only to airflow limitation but also to the clinical control of asthma,” Fujisawa and colleagues remark.

Indeed, they found that scores on the Asthma Control Test (ACT) negatively and significantly correlated with plasma CTGF levels.

The fact that CTGF levels correlated with both clinical and physiological parameters will “ensure the usefulness of plasma CTGF level as a clinical biomarker of asthma”, says the team.

To detect the plasma N-terminal CTGF levels, the researchers used a simple method, whereby the full length CTGF level was subtracted from the total CTGF level, both of which had been determined from sandwich enzyme-linked immunosorbent assays using anti-CTGF antibodies.

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