No data are currently available in France on the prevalence of positive serological responses in cystic fibrosis patients. Serological analyzes of the sera collected during this study will enable us to evaluate the performance of serology in mycobacterial culture and to identify patients with no positive respiratory specimen in culture but with positive serology indicating potential contact with a mycobacterium. The establishment of a serological follow-up of these patients will allow to correlate this result with a clinical evolution and / or the detection of NTM in subsequent samples. Serology is an innovative aspect of the CIMENT study.