Sputum culture has been the best approach to detect harmful bacteria in the lungs of people with cystic fibrosis (CF). With the widespread use of new CF therapies (like Trikafta and Alyftrak), it is more difficult for people with CF to produce sputum even though they still have harmful bacteria in their lungs. The SEND-CF study is being done to see if there are other ways to detect harmful bacteria in the lungs.

People with cystic fibrosis (CF) often get lung infections that can make their breathing worse and make their lungs weaker over time. Sputum culture is usually analyzed to find these infections. Currently, many people with CF are using CFTR modulators. These medicines help, but they also make it harder for people to cough up sputum. Even though people with CF are making less sputum, lung infections are still a problem. New ways are needed to check for infections without using sputum.

The SEND-CF study wants to gather health information and samples from people with CF in order to find new and better ways to spot harmful bacteria in the lungs. Participants, who typically are able to produce sputum who consent to participate will be asked to provide samples including sputum, saliva, serum, plasma, buffy coat, urine, and whole blood. Some participants will also provide breath samples for a sub-study.

Inclusion Criteria:

• ≥ 16 years of age on day of study visit
• Documentation of CF Diagnosis
• Able to expectorate sputum
• Percent predicted FEV1 ≥ 30%

Exclusion Criteria:

• History of solid organ transplantation
• History of active malignancy (or treatment for malignancy) in 12 months prior to the study visit
• Pregnant

Study participants will be recruited at Cystic Fibrosis Foundation's Therapeutics Development Network study sites