Attenuated C-reactive protein response to infection in newborns and neonates: an age-stratified analysis in children with sepsis.

Purpose: C-reactive protein (CRP) is widely used to guide antibiotic therapy in children; however, a uniform CRP cut-off is commonly applied across all pediatric age groups. This study aimed to investigate whether the CRP response to infection differs by age in children with sepsis. Methods: This single-center retrospective cross-sectional study included children with a discharge diagnosis of sepsis. Patients were stratified into five age groups according to the recommendations of the International Pediatric Sepsis Consensus Conference: newborn (0 < age ≤ 7 days), neonate (7 < age ≤ 30 days), infant (30 days < age ≤ 2 years), toddler/preschool (2 < age ≤ 6 years), and school age/adolescent (6 < age < 18 years). Demographic characteristics, disease severity, vital signs, laboratory parameters, and microbiological test results were collected. Associations between CRP and other parameters were analyzed within and across age groups using nonparametric methods. Results: A total of 1,228 patients were included. Newborns and neonates had the highest disease severity (vasoactive infusion: 50.0% and 17.7%; invasive ventilation: 56.5% and 24.2%), yet the lowest CRP levels (median 2.32 mg/L and 5.09 mg/L). In contrast, older children had markedly lower disease severity but 5 to 10-fold higher CRP levels. CRP was positively correlated with procalcitonin (PCT) across all age groups ( Conclusion: The CRP response to infection is substantially attenuated in newborns and neonates despite greater clinical severity. This age-dependent phenomenon suggests that a single CRP cut-off is inappropriate for all pediatric age groups. Clinicians should interpret CRP levels in very young children with caution, recognizing that even modest elevations may indicate clinically significant infection.