Serum Clara cell 16-kDa protein levels and lung impairment in systemic sclerosis patients

To assess clinical utility of serum Clara cell 16-kDa protein measurements in relation with staging system for systemic sclerosis associated interstitial lung disease.

Serum levels of Clara cell 16-kDa protein were determined by ELISA in 28 systemic sclerosis patients and 30 healthy controls, and correlated with staging system for systemic sclerosis associated interstitial lung disease in systemic sclerosis patients. Lung involvement was assessed functionally (body plethysmography, diffusing capacity of the lung for carbon monoxide) and radiologically (an average disease extent on high resolution computed tomography of the lungs) in SSc patients.

We observed statistically significant differences in serum Clara cell 16-kDa protein levels between systemic sclerosis patients and healthy controls only in non-smokers. However, serum Clara cell 16-kDa protein concentrations were significantly elevated in patients with high resolution computed tomography extent >20% in comparison to patients with high resolution computed tomography extent <20% (p=0.01). They correlated positively with average disease extent on high resolution computed tomography (p=0.04), an extent of a reticular pattern on high resolution computed tomography (p<0.01), and negatively with a total lung capacity (p=0.03) and the results of the 6-min walk test (p<0.01).

Clara cell 16-kDa protein levels can be considered as a supplemental serum biomarker for systemic sclerosis associated interstitial lung disease.