Data collection
At admission, the patients’ parents were asked whether they smoked, whether the parents were atopic, and whether the patient had siblings or went to nursery school.
A thoracic X-ray examination and a blood test were performed. Procalcitonin (PCT) was quantified by electrochemiluminescence with the Cobas e-411® analyzer (Roche). C-reactive protein (CRP) was quantified by the CRP Flex method (Dimension Vista, Siemens).
The following microbiological samples were collected from all patients: RSV antigen, multiple CRP for respiratory viruses (PneumoVir) from a nasal swab, blood culture, and a urine culture.
In patients requiring IMV, an endotracheal aspirate (ETA) sample was collected at intubation. Proven bacterial coinfection was defined as >100,000 colony-forming units/mL (CFU/mL), and bronchial tree colonization as ≤100,000 CFU/mL.
At discharge, data on the number of days of therapy required, and the need for nasal cannulas, high-flow oxygen therapy (HFOT), noninvasive mechanical ventilation (NIMV), and IMV were collected.
In patients with suspected sepsis or PCT ≥0.5 ng/mL and in patients requiring IMV, antibiotic therapy was initiated according to the PICU’s AB protocol.
Bronchiolitis severity was established by the need for and duration of IMV as well as by PICU length of stay.