This is a intervention longitudinal study for children with CF and caregivers. Children aged 2-5 who are diagnosed with CF and are eligible for TRIKAFTA will be invited to participate in this study. The treating physicians will manage children with CF in accordance to their medical judgement and data will be collected throughout the study. Children with CF and caregivers may be enrolled up to 3 months before their child initiates TRIKAFTA and site personnel will record date for the study in that time (such as pulmonary exacerbations, medical history, and medication history.) Caregivers will also report PROS (patient reported outcomes) and CGRO (caregiver-reported outcomes).

This is an observational study which will collect sweat chloride values from approximately 1000 cystic fibrosis subjects who are currently on cystic fibrosis transmembrane conductance regulator (CFTR) modulators. This study will require one visit to an MUSC clinic which will last approximately 2 hours. Compensation is provided.