Neutrophil percentage-to-albumin ratio and its discriminative performance in pneumonia-associated sepsis and septic shock in children older than 3 years: a retrospective observational study

Purpose Neutrophil percentage (N%) and albumin (ALB) are associated with sepsis. We investigated the association between the neutrophil percentage-to-albumin ratio (NPAR) and pneumonia-associated sepsis and septic shock in children, and evaluated its discriminative performance for these conditions. Methods This retrospective observational study began with children aged >3 years admitted to Henan Children's Hospital (2021–2024) with septic shock. Among them, 88 children with pneumonia-associated septic shock formed the index (anchor) group, and each was matched 1:1 on sex, age, admission year and admission month to one child with pneumonia and sepsis without shock and to one child with pneumonia but without sepsis (88 per group). The sepsis cohort comprised the sepsis without shock and septic shock groups. NPAR was calculated from the first laboratory results within 24 h of admission. Sepsis status and severity were classified using the Phoenix Sepsis Score (PSS) at the same admission, without follow-up. Results NPAR was higher in children with sepsis than in those with non-sepsis pneumonia and higher in septic shock than in sepsis without shock (both P < 0.001), and was independently associated with PSS-defined sepsis and septic shock after adjustment for clinical and laboratory covariates. In this cohort, NPAR showed exploratory discrimination for sepsis (area under the curve [AUC] 0.83, 95% confidence interval [CI] 0.78–0.88) and septic shock (AUC 0.77, 95% CI 0.71–0.83). For sepsis, its AUC exceeded those of N%, ALB and C-reactive protein (CRP); for septic shock, it exceeded N% and CRP but not ALB (0.77 vs. 0.76, P = 0.819). The proposed thresholds (1.75 for sepsis and 1.87 for septic shock) are exploratory and require external validation. Conclusions NPAR is elevated in pediatric pneumonia-associated sepsis and septic shock and may help to discriminate these conditions. These findings are retrospective and exploratory and reflect an association with sepsis severity at presentation rather than prediction of subsequent deterioration; the proposed thresholds require external validation before clinical use.