Material and methods
This is an ambispective, observational, descriptive, and comparative clinical research study to determine the association between levels of specific immunoglobulin A against respiratory syncytial virus (RSV) and clinical characteristics in pediatric patients infected with this virus. There were included all hospitalized pediatric patients younger than 5 years old with a diagnosis of RSV pneumonia by Luminex multiple molecular assay and RT-PCR according to the CDC Atlanta protocol, identified within the Clinical Microbiology laboratory from the period of 2014 to 2017, as well as respiratory samples (nasopharyngeal exudate / bronchioalveolar lavage) from infected children in the period from August 2018 to August 2019 at the National Institute of Respiratory Diseases (INER). There were considered non-inclusion criteria all patients who were diagnosed with RSV infection in another laboratory, who were not found in the age limit, as well as all those patients for whom it was not achieved to complete the samples or information necessary to meet the objectives of this study.