Cord Blood Biomarkers Show Promise for Early Risk Stratification in Neonatal Encephalopathy, Meta-Analysis Finds
Key Insights
A systematic review and meta-analysis of 63 studies found neonates with neonatal encephalopathy (search) (NE) have significantly elevated umbilical cord blood levels of multiple neuronal injury, inflammatory, and oxidative stress biomarkers compared to controls.
Key biomarkers including GFAP, NSE, S100B, activin-A (search), tau, NFL, IL-6, IL-1, TNF-α, troponin, CK-MB, NGAL, MDA, and hypoxanthine were all significantly higher in NE cases, with S100B and IL-6 also elevated in moderate/severe versus mild NE.
The findings suggest cord blood biomarkers may aid early risk stratification and identification of candidates for adjunctive neuroprotective therapies, though clinical utility is limited by methodological heterogeneity and lack of consistent neurodevelopmental outcome correlation.
A comprehensive systematic review and meta-analysis published in Pediatric Research has identified multiple umbilical cord blood biomarkers that are significantly elevated in neonates with neonatal encephalopathy (search) (NE), offering potential tools for early risk stratification in this vulnerable population. The analysis, encompassing 63 studies and over 6,100 neonates, represents one of the most extensive evaluations to date of cord blood biomarkers specifically for NE.
The meta-analysis, which included 49 studies with quantitative data, found that neonates with NE had significantly higher cord blood levels of neuronal injury markers—including glial fibrillary acidic protein (GFAP) (search), neuron-specific enolase (NSE) (search), S100 calcium-binding protein B (S100B) (search), activin-A (search), neuronal protein tau, and neurofilament light chain (NFL) (search)—compared to healthy controls. Inflammatory markers interleukin (IL)-6, IL-16, IL-1, tumor necrosis factor-alpha (TNF-α) (search), and nucleated red blood cells (NRBC) were also significantly elevated, as were markers of oxidative stress, cardiac injury, vascular stress, and lipid peroxidation.
Neuronal Injury Markers Show Consistent Elevation
Among the neuronal injury biomarkers, GFAP levels were significantly higher in NE cases compared to controls (Z = 2.76, p = 0.006), based on a meta-analysis of five studies. NSE was also significantly elevated (Z = 2.36, p = 0.02) across three studies, as was S100B (Z = 2.99, p = 0.003) across five studies. Notably, activin-A (search) demonstrated the strongest statistical association, with significantly higher levels in NE neonates (Z = 4.85, p < 0.00001) based on three studies.
Neuronal protein tau (Z = 2.58, p = 0.010) and NFL (Z = 3.56, p = 0.0004) were each significantly elevated in NE cases based on meta-analyses of two studies each. Secretoneurin, netrin-1, and brain-derived neurotrophic factor (BDNF) were also reported as higher in NE neonates, though these findings came from single studies.
Inflammatory and Oxidative Stress Cascades Activated
The inflammatory cytokine IL-6 was significantly elevated in NE cases (Z = 3.83, p = 0.0001) across five studies, and a subgroup analysis of three studies using the same measurement method confirmed this finding (Z = 3.08, p = 0.002). IL-16 (Z = 3.28, p = 0.001) and IL-1 (Z = 3.28, p = 0.001) were similarly elevated, each based on three studies. TNF-α showed a robust association (Z = 8.05, p < 0.00001) across two studies, while NRBC levels were markedly higher in NE neonates (Z = 5.28, p < 0.00001) based on eight studies.
Oxidative stress markers also distinguished NE cases from controls. The prooxidant-antioxidant balance (PAB) was significantly elevated (Z = 7.55, p < 0.00001) across two studies, and malondialdehyde (MDA), a marker of lipid peroxidation, was significantly higher (Z = 3.60, p = 0.0003) across three studies.
Severity Stratification Potential
The analysis also examined whether biomarkers could differentiate between moderate/severe and mild NE. S100B levels were significantly higher in neonates with severe compared to mild NE (Z = 3.17, p = 0.002) based on two studies. IL-6 was similarly elevated in severe versus mild cases (Z = 2.43, p = 0.02) across three studies, with a subgroup analysis of two studies using the same method confirming this finding (Z = 2.36, p = 0.02).
Clinical Utility and Cautions
Despite the breadth of positive findings, the authors urge caution in clinical interpretation. "Cord blood biomarkers should not be interpreted as replacements for established clinical diagnostic criteria for NE, which remain based on neurological examination, biochemical parameters, and eligibility for therapeutic hypothermia," the researchers note. In most included studies, neonates had already fulfilled criteria for NE, limiting the incremental diagnostic value of these biomarkers.
Instead, the potential role of cord blood biomarkers lies in early risk stratification, severity assessment, and identification of candidates for adjunctive neuroprotective therapies, particularly in research settings. "Identifying biomarkers that reflect early neuronal injury, inflammation, and oxidative stress may be valuable for enriching study populations in future neuroprotective trials and for identifying infants most likely to benefit from adjunctive therapies beyond therapeutic hypothermia," the authors write.
Significant Limitations Acknowledged
The review identified substantial methodological heterogeneity across studies, including variations in biomarker assay platforms ranging from enzyme-linked immunosorbent assays (ELISA) to ultrasensitive digital platforms such as Simoa. These methods "differ markedly in analytical sensitivity, specificity, dynamic range, and lower and upper limits of detection," the authors note, and values falling below or above assay detection thresholds were inconsistently reported.
A major limitation is the lack of consistent correlation between cord blood biomarker levels and clinically meaningful outcomes, including MRI-defined brain injury and long-term neurodevelopmental impairment. "Without such associations, it remains unclear whether these biomarkers provide prognostic value beyond existing clinical tools," the researchers state.
Furthermore, many of the identified biomarkers—including inflammatory cytokines and oxidative stress markers—are not specific to brain injury and may reflect a broader systemic hypoxic-ischemic or inflammatory response. The authors also highlight that most studies did not specify whether cord blood samples were obtained from the umbilical artery, vein, or mixed sources, despite known physiological differences between these compartments.
The researchers call for future studies to incorporate standardized neuroimaging scoring systems and longitudinal neurodevelopmental follow-up, and suggest that "a battery of both specific and non-specific biomarkers will likely yield the highest results" in clinical practice.