Association between CFTR modulators and changes in iron deficiency markers in cystic fibrosis

•Iron deficiency is a common comorbidity in cystic fibrosis, despite CFTR modulators.•Highly-effective modulator therapy is associated with improved iron deficiency labs.•CFTR modulator therapy is associated with improved hemoglobin.•Sex differences exist in iron deficiency in cystic fibrosis. Iron deficiency (ID) is a common extrapulmonary manifestation in cystic fibrosis (CF). CF transmembrane conductance regulator (CFTR) modulator therapies, particularly highly-effective modulator therapy (HEMT), have drastically improved health status in a majority of people with CF. We hypothesize that CFTR modulator use is associated with improved markers of ID. In a multicenter retrospective cohort study across 4 United States CF centers 2012–2022, the association between modulator therapies and ID laboratory outcomes was estimated using multivariable linear mixed effects models overall and by key subgroups. Summary statistics describe the prevalence and trends of ID, defined a priori as transferrin saturation (TSAT)