Introduction: Lung ultrasound (LUS) is increasingly used in respiratory care for diaphragmatic evaluation and parenchymal description. Considering its performance and safety, we aimed to evaluate its usefulness on adult cystic fibrosis (CF) patients follow-up. 

Objectives: To evaluate LUS sensitivity to change in patients starting a treatment by ELEXACAFTOR-IVACAFTOR-TEZACAFTOR or IVACAFTOR-TEZACAFTOR in the adult CF population. 

Methods: We conducted a retrospective national multicenter observational study from 01/09/2021 to 30/06/2022 in 7 french hospitals. FEV1, Chest X-ray (CX) Norman-Crispin score and LUS score were collected at M0, M1 and M3 after introduction of the treatment. The LUS score, ranging from 0 to 7, rated the number of B lines, their coalescence, irregularities in the aerated pleuropulmonary line, the presence and size of condensations, the presence of pleural effusion and the fraction of diaphragm thickening.

Results: Interim analysis included 32 patients. The mean ± SD LUS score was estimated at 1.70 ±0,94 at baseline, 1.20 ±0.69 at M1, and 1.12 ±0,97 at M3. The standardized mean difference (SMD) between M0 and M3, was significant for LUS score -0.66 [95% CI: -1.08; -0.23] (p=0,005), CX score -0.62 [95% CI: -1.03; -0.20] and FEV1 0.60 [95% IC: 0.41; 0.78]. Correlations with LUS score with FEV1 (R=-0.10, [95% CI: -0.43; 0.26]) and CX score (R=0.09, [95% CI: -0.26; 0.43]) were not significant.

Conclusion: LUS has a fair sensitivity to change. The weak correlation of CX with LUS suggests that they give different information and one cannot replace the other. Follow-up is continuing at M6 and at M12.