High levels of a blood protein called CC16 predict a higher likelihood of lung disease worsening in patients with systemic sclerosis (SSc), according to researchers.
Their study, “High Baseline Serum Clara Cell 16 kDa Predicts Subsequent Lung Disease Worsening in Systemic Sclerosis,” was published in The Journal of Rheumatology.
Clara cell 16 kDa (CC16) is a pneumoprotein (a protein produced by the lung) and a known sensitive biomarker of lung damage.
In the presence of acute or chronic lung injuries, CC16 is released into the bloodstream, and therefore its serum levels reflect the extension of lung damage. In line with this observation, levels of this protein are known to be high in the blood of patients with pulmonary fibrosis.
In the study, researchers reasoned that, since elevated serum levels of CC16 could identify lung damage, they might be used to predict the rate of lung function worsening in patients with systemic sclerosis.
To test this hypothesis, researchers set up a prospective study that followed 106 patients (mean age of 55.4) with systemic sclerosis for four years. About half of the patients (52.8%) had interstitial lung disease (ILD), while about one-third (35%) displayed diffuse cutaneous scleroderma.
The risk of lung disease progression was analyzed throughout the four-year period — defined as a 10% decrease in the total lung capacity or forced vital capacity, or death — and compared with the serum CC16 levels at baseline, when patients were included in the study.
Results showed that a blood level of the protein higher than 33 ng/mL predicted deterioration of lung disease or death within two years, with a 76% sensitivity and 65% specificity.
Patients with higher baseline serum CC16 levels experienced, on average, an event of lung disease worsening or death earlier (42.8 months) than patients with low baseline serum levels (56.3 months).
Even after adjusting the results for age, duration of disease, clinical, and lung function measures, patients with elevated levels were at a higher risk (2.9 times higher) of more rapid lung disease worsening, when compared with patients with levels below 33 ng/mL.
“Our findings showed that baseline serum CC16 has a significant predictive value for worsening of lung disease in patients with [systemic sclerosis],” the researchers wrote.
“Further studies are needed to show whether serum CC16 could be used in association with other pneumoproteins to obtain a better predictive value in SSc and other chronic pulmonary diseases,” they added.