Pathogen Identification in Pediatric Hematopoietic Stem Cell Transplant Patients With Suspected Lower Respiratory Tract Infection

Inclusion Criteria: * Patients will be ≤21 years of age with a history of HCT of any type at any point in the past, and are planned to undergo clinically-indicated collection of any lower respiratory specimen, including but not limited to bronchoalveolar lavage (either via a plugged telescoping catheter such as a CombiCath, or with fiberoptic bronchoscopy) and tracheal aspirate. * For the purposes of this study, induced or spontaneous sputum is not considered a lower respiratory tract specimen. * Patients may have any underlying indication for clinical testing of lower respiratory secretions, including but not limited to suspected infection, non-infectious inflammation, obstructive or restrictive lung disease, pulmonary edema, pleural effusions, alveolar hemorrhage, aspiration, or pulmonary vascular disease. * Patients who have not undergone HCT but plan to undergo HCT in the future, hereafter referred to as pre-HCT patients, may also be enrolled. * Pre-HCT patients must have intention to undergo stem cell transplantation in the future and include but are not limited to patients with primary immunodeficiency, patients with malignancy undergoing induction or consolidation chemotherapy, and HCT patients with selected cell sources who are undergoing pre-transplant conditioning but have not yet received their cellular infusion. Exclusion Criteria: * Patients will not be \>21 years of age. * Patients who do not have a clinical indication for obtaining lower respiratory secretions for testing as part of their direct patient care will be excluded. * Patients who do not have sufficient respiratory secretions remaining after collection and aliquoting for indicated clinical tests ordered by the treating clinician will also be excluded. * Patients who undergo lower respiratory testing solely to evaluate for relapsed malignancy will be excluded.