Table 4.

NEC-relevant NET biomarkers and auxiliary assessment technologies.

Marker/technology	Sample	What it may indicate	Strengths	Main limitations
cfDNA/nucleosomes	Serum/plasma	Cell death, chromatin release, possible NETs	Easy, dynamic	Nonspecific; hemolysis, necrosis, apoptosis, platelets
H3cit	Blood/tissue	PAD4-dependent histone citrullination	Mechanistically specific for one NET pathway	Misses PAD4-independent NETs; timing sensitive
MPO-DNA/NE-DNA complexes	Blood	Granule proteins complexed with extracellular DNA	Closer to NETs than cfDNA	Degranulation plus non-NET DNA; assay/platform variability
Tissue DNA-MPO/NE-H3cit co-localization	Surgical/biopsy tissue	Local NET structures and spatial relationship to injury	Strong spatial evidence	Usually late disease; sampling and interpretation bias
Fecal calprotectin	Stool	Intestinal neutrophil influx; partially NET-derived	Noninvasive, repeatable	Affected by gestational age, feeding, non-specific enterocolitis
Ultrasound/POCUS and emerging optical/AI tools	Bedside imaging	Wall thickness, blood flow, portal venous gas, fluid; tissue oxygenation	Repeatable, can precede radiographic necrosis	Operator/device dependence; requires validation and NET correlation
Multi-omics + machine learning	Blood/stool/imaging/clinical	Microbial, metabolic, immune, and tissue-injury trajectories	May reveal pre-symptomatic risk	Small cohorts, variable definitions, external validation limited