The objective of study is to prospectively determine if CPET with blood gas analysis should have a prognostic value in CF. The study plans to include 300 cystic fibrosis patients. Inclusion criteria will be: age >15 years, cystic fibrosis confirmed by chloride sweat test or genetic analysis, clinical and functional stability in the 2 month before CPET. Patients will perform a maximal exercise test on a cycloergometer during the inclusion visit, with pulmonary function testing and a six-minute walk test. The study will also include a visit every 6 months with: body mass index calculation, pulmonary function testing with DLCO (diffusing lung capacity for carbon monoxide), a six minute walk test, and antibacteriological study of sputum. The results of this study could help identify earlier the patients for referral to a lung transplantation centre, by using the usual criteria and the CPET abnormalities.

Current guidelines for referring cystic fibrosis (CF) patients for lung transplantation, based on clinical and functional resting parameters, are insufficient to predict 3-year mortality. Previous studies have shown that sex, impaired pulmonary function, undernutrition and colonization of the respiratory tract by Pseudomonas aeruginosa are associated with a poor prognosis. Current guidelines for referral to a lung transplant center include age, sex, forced expiratory volume at one second (FEV1) below 30% predicted or a rapid decline of FEV1, in particular in young female patients, increasing frequency of exacerbations requiring antibiotic therapy, refractory or recurrent pneumothorax, recurrent hemoptysis not controlled by embolization. But, despite these criteria, near that 30% of patients are still dying while on the lung transplant waiting list, or are transplanted in high emergency. Cardiopulmonary exercise testing (CPET) in CF patients would have an interest in the following of cystic fibrosis patients. A previous study, carried out on fifty one adult patients, showed that CPET with blood gas analysis may have a prognosis value in cystic fibrosis. The authors found that a BMI < 19.8 and P(A-a)O2 peak > 43 mmHg were independently associated with a lower chance of survival.

Inclusion Criteria:

• Age more than 15 years
• Cystic fibrosis diagnosed by positive sweat chloride test or genetic test

Exclusion Criteria:

• Pregnant or breastfeeding woman
• waiting on transplantation list