2.1-Study design, sites, and subjects
We performed a single-center retrospective study of children under five years of age hospitalized with a clinical diagnosis of LRTI, presenting to the emergency department, outpatient clinics (pediatric pulmonology, pediatrics, pediatric infectious disease), or ICU of Ege University Medical Faculty Children Hospital from January 2010 through January 2020. The hospital institutional review board approved this study.
The study institution’s standard practice is to screen all admitted patients with respiratory symptoms for viral respiratory pathogens. Because the International Classification of Diseases discharge codes might be inaccurate coding or misdiagnosis on the part of the treating clinician, cases were identified by evaluating the virology laboratory database. Subsequently, we cross-checked the virology laboratory results with electronic medical records and nurse observation charts. According to the revised World Health Organization guidelines11, patients between 1-60 months of age who clinically fulfilled the criteria of LRTI (pneumonia or bronchiolitis) were included in the study. Exclusion criteria included hospitalization within the preceding 30 days, other diagnoses than LRTI caused by respiratory viruses, hospital-acquired viral LRTI, primary (defined as bacterial growth detected in cultures from sterile cavities such as blood, cerebrospinal fluid, urine, and pleural fluid) or secondary (defined as bacterial growth in cultures taken from sterile cavities 48 hours after hospitalization)12 bacterial infections, newborns (under one month of age), and incomplete medical records.