Improving P. Aeruginosa Detection With Breath-based Diagnostics (IMPACT-Breath)

Inclusion Criteria: * Aim 1, Cross-Sectional IInclusion Criteria: 1. Male or female, ages 8 years and older 2. Diagnosis of CF based on sweat chloride ≥ 60 mmol/L and/or 2 known CF mutations 3. @ BC Children's Hospital only- Non-expectorators are eligible if having a clinically indicated OP swab. 4. FEV1 ≥ 30% predicted for spontaneous expectorators or FEV1 ≥ 40% predicted for subjects undergoing sputum induction 5. Either P. aeruginosa (Pa) negative or chronically infected with P. aeruginosa (Pa positive) as defined below: a. P. aeruginosa negative: must meet one of the following criteria: i: No growth of Pa in previous 12 months and ≥ 4 consecutive Pa-negative cultures, OR ii: No history of Pa positive airway cultures (sputum, OP, Bronchoalveolar lavage) b. P. aeruginosa positive i: Over 50% of cultures positive and at least 2 cultures positive for Pa in previous 18 months 6. Willing to participate in and comply with the study procedures and willingness of the subject, parent or legally authorized representative to provide written informed consent. Exclusion criteria: 1. Age \< 8 years 2. Intermittently infected with Pa 3. FEV1 \< 30% 4. History of lung transplant 5. Presence of a condition or abnormality that in the opinion of the Principal Investigator would compromise the safety of the subject or the quality of the data. Aim 2, Longitudinal Inclusion Criteria, Expectorating Cohort (n=48): 1. Male or female, ages 8-16 years 2. Diagnosis of CF based on sweat chloride ≥ 60 mmol/L and/or 2 known CF mutations 3. @ BC Children's Hospital only- Non-expectorators are eligible if having a clinically indicated OP swab. 4. FEV1 ≥ 30% predicted for spontaneous expectorators or FEV1 ≥ 40% predicted for subjects undergoing sputum induction 5. P. aeruginosa negative, based on one of the following criteria: 1. No growth of Pa in previous 12 months and ≥ 4 consecutive Pa-negative cultures 2. No history of Pa positive airway cultures (sputum, OP, bronchoalveolar lavage) 6. Willing to participate in and comply with the study procedures and willingness of the subject, parent or legally authorized representative to provide written informed consent. Exclusion criteria: 1. Age \< 8 years 2. Intermittently or chronically infected with Pa 3. Unable to expectorate sputum or undergo sputum induction 4. FEV1 \< 30% 5. History of lung transplant 6. Presence of a condition or abnormality that in the opinion of the Principal Investigator would compromise the safety of the subject or the quality of the data. Inclusion Criteria, Non-Expectorating Cohort (n=10): 1. Male or female, ages 3-8 years 2. Diagnosis of CF based on sweat chloride ≥ 60 mmol/L and/or 2 known CF mutations 3. FEV1 ≥ 30% 4\. Unable to expectorate sputum 5. P. aeruginosa negative, based on one of the following criteria: 1. No growth of Pa in previous 12 months and ≥ 4 consecutive Pa-negative cultures 2. No history of Pa positive airway cultures (sputum, OP, bronchoalveolar lavage) 6. Willing to participate in and comply with the study procedures and willingness of the subject, parent or legally authorized representative to provide written informed consent. Exclusion criteria: 1. Age \< 3 years 2. Intermittently or chronically infected with Pa 3. FEV1 \< 30% 4. History of lung transplant 5. Presence of a condition or abnormality that in the opinion of the Principal Investigator would compromise the safety of the subject or the quality of the data.