Changes in fecal elastase-1 following initiation of CFTR modulator therapy in pediatric patients with cystic fibrosis

•Age was negatively correlated with change in FE-1.•21% had post-modulator FE-1 values ≥200 mcg/g, consistent with pancreatic sufficiency.•Significant increase in FE-1 from median 25 mcg/g at baseline to 57 mcg/g post-modulator.•Absolute change in fecal elastase-1 of median 28 mcg/g and mean of 93.5 mcg/g.•The pancreatic sufficient group was a younger age at first CFTR modulator and had a higher baseline fecal elastase-1. Improvement in exocrine pancreatic function in persons with CF (pwCF) on cystic fibrosis transmembrane conductance regulator (CFTR) modulators has been documented in clinical trials using fecal pancreatic elastase-1 (FE-1). Our group endeavored to evaluate real-world data on FE-1 in children on CFTR modulator therapy at three pediatric cystic fibrosis (CF) centers. Pediatric pwCF were offered FE-1 testing if they were on pancreatic enzyme replacement therapy (PERT) and on CFTR modulator therapy according to their center's guideline. FE-1 data were collected retrospectively. The primary outcome was absolute change in FE-1. 70 pwCF were included for analysis. 53 had baseline and post-modulator FE-1 values. There was a significant increase in FE-1 from median 25 mcg/g (IQR 25–60) at baseline to 57 mcg/g (IQR 20–228) post-modulator (p