High Baseline Serum Clara Cell 16 kDa Predicts Subsequent Lung Disease Worsening in Systemic Sclerosis

Abstract

Objective: Clara cell secretory protein (CC16) is a sensitive marker of bronchial epithelial cell damage. The CC16 serum level is elevated in patients with pulmonary fibrosis, but its predictive value on lung disease progression has not yet been studied. We aimed to assess the value of serum CC16 concentration in predicting lung disease deterioration in patients with systemic sclerosis (SSc).

Methods: We prospectively analyzed and followed 106 patients with SSc during a 4-year period for the risk of developing combined deleterious event, defined as a 10% decrease in total lung capacity or forced vital capacity from baseline, or death, according to serum CC16 at inclusion. Receiver-operating characteristic (ROC) curve analysis was performed for prediction of events during the first 2 years after inclusion. Cumulative risks of combined events were computed by Kaplan-Meier analysis.

Results: The best cutoff level of serum CC16 for prediction of a combined event was 33 ng/ml, with 76% sensitivity and 65% specificity (area under the ROC curve: 0.71, 95% CI 0.61-0.81, p < 0.0001). Progression of lung disease evaluated by a mean time-to-event differed between patients with high baseline serum CC16 (42.8 mos, 36.3-49.3) and those with low serum CC16 (56.3 mos, 50.9-61.7; log-rank test, p < 0.001). After adjustment for age, duration of disease, clinical and lung function measures, the risk of combined event occurrence in patients with high serum CC16 was significantly higher than in those with low CC16 (HR 2.9, 1.2-6.75, p < 0.05).

Conclusion: High baseline serum CC16 predicts lung disease worsening in patients with SSc.

Keywords: CLARA CELL SECRETORY PROTEIN; INTERSTITIAL LUNG DISEASE; LUNG FUNCTION; PROGNOSIS; SYSTEMIC SCLEROSIS.