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 IL‑6 shows promise as a powerful diagnostic biomarker for sepsis in neonates, children, and pregnant women, outperforming in-use biomarkers in a study.

Interleukin‑6 (IL‑6) shows potential as a powerful diagnostic biomarker for sepsis in neonates, children, and pregnant women—outperforming in-use biomarkers in a real‑world cohort, according to research unveiled at ESCMID Global 2025.

“Biomarkers may be useful adjuncts to clinical assessment in the diagnosis of pediatric, maternal, and neonatal sepsis,” wrote Seán O. Whelan, PhD, of Children’s Health Ireland at Temple Street, and colleagues. “Traditional biomarkers like C-reactive protein (CRP) and procalcitonin (PCT) are sub-optimally sensitive and limited by delayed response to infectious stimuli.”

The researchers investigated the diagnostic performance of serum IL-6 compared to in-use biomarkers in neonates, children, and pregnant women.

Study Design & Cohort Selection

The authors conducted a retrospective cohort analysis spanning one year at a specialist children’s hospital and a maternity hospital. All patients who underwent IL‑6 testing for suspected sepsis during that interval were enrolled, yielding 252 cases: 111 pediatric, 72 maternity, and 69 neonatal. Patients were classified along two axes—­etiology (bacterial, viral, no infection) and physiological normal, systemic inflammatory response syndrome, sepsis, and septic shock)—using predefined criteria. Serial samples enabled kinetic profiling. IL‑6, CRP, PCT, and the neutrophil‑to‑lymphocyte ratio (NLR) were benchmarked via area under the receiver operating characteristic curve (AUROC) and diagnostic indices at empirically derived cut points.

Kinetic & Diagnostic Superiority of IL‑6

According to findings, IL‑6 emerged as the only marker whose median concentrations differed significantly across all etiological and physiological strata in every population. Whereas CRP, PCT, and NLR continued to climb on repeat sampling, IL‑6 increased within 1-2 hours and peaked at 6 hours, making IL-6 a promising biomarker for earlier clinical intervention, explained the researchers

Additionally, IL‑6 yielded the highest AUROCs across cohorts, surpassing all comparators for both physiologic and etiologic sepsis endpoints for pediatric patients, outperforming other markers for the analogous maternal outcomes (except NLR), and eclipsing every marker but PCT for the neonatal endpoint. For pediatric patients, IL‑6 achieved an AUROC of 0.91 (cut point 43.6 pg/mL) for discriminating bacterial from non‑bacterial infection; corresponding values were even stronger in pregnant women (AUROC 0.94, cut point 40.2 pg/mL).

Clinical Implications & Future Directions

“Our findings reinforce the potential of IL-6 as a promising biomarker in sepsis diagnosis,” said Dr. Whelan during his study abstract presentation at ESCMID Global 2025. “With wider adoption and in combination with clinical assessment, IL-6 could significantly improve clinical decision-making and support timely, targeted treatment for high-risk patients.”

The authors concluded with a recommendation for “further prospective study of the impact on patient outcomes.”