Kinetics of YKL-40 Protein in Serum of Cystic Fibrosis Patients

YKL-40 is proposed as a biomarker of various inflammatory disease diabetes and lung disease including cystic fibrosis. In those cross-sectional studies, a unique value of YKL-40 is used to correlate with clinical, physiological, or biological determinants of disease severity (like FEV1 for example in lung disease). There is only one longitudinal study that showed a correlation between circulating levels of YKL-40 and the decline of lung function in smokers sampled from the general population. In order to better understand the potential role of YKL-40 in CF pathophysiology, and to determine its potential role as a biomarker of disease evolution, it is essential to proceed with further clinical evaluation. The investigators propose to perform an observational prospective cohort study to determine if variation of YKL-40 concentration over 24 months correlates with the clinical evolution of the patients.