Clinical Research Directory

Inclusion Criteria: 1. Written parental informed consent and assent obtained from subject and the subject's legal guardian. 2. Be willing and able to adhere to the study visit schedule and other protocol requirements. 3. All genders 6-11 years old on Day 1. 4. Diagnosis of CF. 5. CFTR mutations consistent with the FDA labeled indication for the ETI. 6. Physician intent to prescribe the ETI. 7. Able to attempt the testing and procedures required for this study, as judged by the investigator. 8. Enrolled in the Cystic Fibrosis Foundation Patient Registry. 9. Clinically stable with no significant changes in health status within the 14 days prior to Visit 1 (and inclusive of Visit 1). Exclusion Criteria: 1. Has any other condition that, in the opinion of the Site Investigator/designee, would preclude informed consent or assent, make study participation unsafe, complicate interpretation of study outcome data, or otherwise interfere with achieving the study objectives. 2. Use of any ETI within the 180 days prior to Visit 1. 3. Any acute use of antibiotics (oral, inhaled or IV) or acute use of systemic corticosteroids within the 14 days prior to Visit 1 (inclusive of Visit 1) for lower respiratory tract symptoms. 4. Initiation of any new chronic therapy (e.g., ibuprofen, Pulmozyme®, hypertonic saline, azithromycin, inhaled tobramycin, Cayston®, Kalydeco, Orkambi®, Symdeko®) within the 4 weeks prior to Visit 1 (inclusive of Visit 1). 5. Use of an investigational agent within the 28 days prior to Visit 1. 6. Use of chronic oral corticosteroids (equivalent to 10 mg. or more per day of prednisone) within the 28 days prior to Visit 1. 7. Treatment for nontuberculous mycobacterial (NTM) infection, consisting of ≥ two antibiotics (oral, IV, and/or inhaled) within the 28 days prior to Visit 1. 8. History of lung or liver transplantation,or listing for organ transplantation.