Introduction: Cystic fibrosis (CF) is an inherited, multisystemic disease. Cystic fibrosis liver disease (CFLD) is the third cause of death in children with CF. Cystic Fibrosis Transmembrane Conductance Regulator modulator (CFTRm) therapies have led to significant improvement of clinical outcomes in patients with CF. However besides the good results on weight and lung function a warning for deterioration of liver function as a side effect of CFTRm therapies is listed.

Aim: The aim of the study is to assess liver function before and after initiation of CFTRm therapies in children.

Methods: Aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and gamma-glutamyl transferase (GGT) were evaluated prior to and post CFTRm therapy.  Liver ultrasound images also were compared. Student t-test was used to analyze the results.

Result: In the study, 83 patients on CFTRm were included. Forty of them were on IVA/LUM and forty-three on ETI. There was no statistically significant difference in the levels of ASAT and ALAT before and after treatment in both groups and no difference in the GGT level prior to and post initiation of ETI. The level of GGT after treatment with IVA/LUM showed a decreasing trend (mean level of GGT before initiation of CFTRm  was 19,5 U/l and after ? 14 U/l, p = 0,029).

Conclusion: We did not identify worsening in the liver status after CFTRm therapy with CTFRm. The results of the study suggest an improvement of liver function after initiation of IVA/LUM. As a limitation of our study  there are not patients with very advanced liver cirrhosis included on CFTRm therapy.