Association Between the Neutrophil-to-Lymphocyte Ratio and Adverse Outcomes in Children Aged

Abstract Background Respiratory syncytial virus (RSV) is a leading cause of hospitalization in children <2 years old. The neutrophil-to-lymphocyte ratio (NLR) is a readily available marker of inflammation that has been studied as a prognostic marker in various infectious diseases. However, its utility in children with RSV remains underexplored. We aimed to determine the association between NLR and adverse outcomes in children <2 years old with RSV. Methods We retrieved records for all clinician-ordered multiplex respiratory viral panel tests for common respiratory pathogens (including RSV) at Vanderbilt University Medical Center between 01/01/2018 and 12/01/2022. We identified RSV-positive children <2 years old who had a complete blood count (CBC) performed with absolute lymphocyte count (ALC) ≥2.00×103/μL and absolute neutrophil count (ANC) ≥1.70×103/μL. Any child with a medical encounter >14 days following a previous encounter was considered a distinct case. We used logistic regression to assess the association between (log-transformed) NLR and adverse outcomes defined as hospitalization, supplemental oxygen use, intensive care unit (ICU) admission, and intubation. Results Of 2,395 RSV-positive children <2 years old, 446 (18.6%) had a CBC performed. Of those, 349 (78.3%) met the stated thresholds for ALC and ANC. The median age of the cohort was 3.7 months (IQR, 1.6–11.6 months), 178 (51.0%) were male, and 269 (77.1%) were hospitalized. Of those hospitalized, 185 (68.8%) received supplemental oxygen, 113 (42.0%) were admitted to the ICU, and 45 (16.7%) were intubated. The odds ratio associated with a two-fold difference in NLR was significant for hospitalization (OR, 1.46; 95% CI, 1.13–1.91; p=0.005) and ICU admission (OR, 1.38; 95% CI, 1.07–1.78; p=0.013) but not for supplemental oxygen use (OR, 1.14; 95% CI, 0.87–1.49; p=0.34) or intubation (OR, 1.32; 95% CI, 0.96–1.83; p=0.092; Table 1). Conclusion Higher NLR was associated with hospitalization and ICU admission in children <2 years with RSV. These findings suggest that NLR has prognostic value in children with RSV.