Background: Bronchiolitis is the most frequent cause of hospitalization in infants younger than 1 year of age. We sought to evaluate the correlation between lymphocyte count and clinical manifestation in infants hospitalized with bronchiolitis.
Materials and methods: We performed a retrospective cohort study evaluating 1297 children hospitalized for bronchiolitis from 2004 to 2019. A nasal washing was tested for 14 respiratory viruses by PCR. A clinical severity score, ranging 0-8, was assigned at hospital admission. History and clinical course were recorded for each infant. Patients were divided in 3 groups according to lymphocyte count tertiles. Parents of enrolled patients have been phoned annually over 5 years in order to evaluate respiratory sequelae.
Results: 433 children had 2914.2±745.5/mm3 lymphocytes (Group 1), 432 had 4897.6±561.5/mm3 lymphocytes (Group 2) and 432 had 7884±1903.3/mm3 lymphocytes (Group 3). Group 1 patients were more frequently infected by RSV and presented with fever, a worse clinical severity score. They more frequently needed oxygen supplementation, underwent a prolonged hospitalization needed to be admitted to pediatric Intensive Care Unit (ICU). Finally, they had more frequently a family history of eczema, wheezing and asthma. We found no differences between lymphocytes count and respiratory sequelae (at least two episodes of wheezing per year).
Conclusions: Infants with low lymphocyte count are more likely to have a worse clinical course of bronchiolitis.