Inflammatory marker profiles in immunocompetent hospitalized children with adenovirus infection and association with hospitalization outcomes.

Background: Adenovirus (ADV) infection can cause substantial systemic inflammation in children, but evidence remains limited regarding early inflammatory marker profiles and their relationship with hospitalization outcomes among immunocompetent hospitalized children. This study investigated inflammatory markers at admission and their associations with length of hospital stay and hospitalization costs, with costs treated as an exploratory secondary economic outcome. Methods: This single-center retrospective observational study consecutively enrolled immunocompetent children hospitalized in the Department of Infectious Diseases, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, from January 1, 2024 to July 31, 2025. Eligible patients had ADV DNA positivity in respiratory specimens within 24 hours after admission, a cycle threshold value ≤35, and clinical findings consistent with acute infection. Demographic data, clinical diagnoses, co-detected pathogens, inflammatory markers, treatment information, length of hospital stay, and hospitalization costs were collected. Between-group comparisons, Spearman correlation analysis, and multivariable linear regression were performed. Results: A total of 145 children were included; 83 (57.24%) were male, and the median age was 61 (36, 84) months. Lower respiratory tract infection was diagnosed in 115 cases (79.31%). ADV mono-infection was identified in 82 cases (56.55%), and co-detection of other pathogens in 63 cases (43.45%). Elevated white blood cell counts (WBCs), C-reactive protein (CRP), ferritin, and interleukin-6 (IL-6) were observed in 54.48%, 85.52%, 53.10%, and 95.86% of patients, respectively, whereas only 2 children had procalcitonin (PCT) ≥2.0 µg/L. Major inflammatory markers did not differ significantly between upper and lower respiratory tract infection groups or between ADV mono-infection and co-detection groups. Interferon-γ was lower in children aged <1 year than in the 1-3-year and 6-12-year groups. The median length of hospital stay was 4 [interquartile range (IQR): 2.5, 6] days, and the median hospitalization cost was 7,950.94 (6,751.66, 10,004.84) yuan. In multivariable analysis, co-detection of other pathogens, IL-6, and interleukin-8 (IL-8) were independently associated with both outcomes. Conclusions: Immunocompetent hospitalized children with ADV infection commonly showed elevated CRP, IL-6, and ferritin, while marked PCT elevation was uncommon. IL-6, IL-8, and co-detection of other pathogens were associated with a longer hospital stay, but their predictive utility and relationship to disease severity were not evaluated. Their associations with hospitalization costs should be interpreted as exploratory economic findings.