Acute Drop in Blood Monocyte Count Differentiates NEC from Other Causes of Feeding Intolerance

OBJECTIVE: Necrotizing enterocolitis (NEC) is characterized by macrophage infiltration into affected tissues. Because intestinal macrophages are derived from recruitment and in situ differentiation of blood monocytes in the gut mucosa, we hypothesized that increased recruitment of monocytes to the intestine during NEC reduces the blood monocyte concentration, and that this fall in blood monocytes can be a useful biomarker for NEC. PATIENTS AND METHODS: We reviewed medical records of very low birth weight (VLBW) infants treated for NEC, and compared them with a matched control group comprised of infants with feeding intolerance but no signs of NEC. Clinical characteristics and absolute monocyte counts (AMC) were recorded. Diagnostic accuracy of AMC values was tested using receiver-operator characteristics (ROC). RESULTS: We compared 69 cases and 257 controls (median 27 weeks, range 26–29 in both groups). In stage II NEC, AMC decreased from median 1.7 × 10(9)/L (interquartile range (IQR) 0.98–2.4) to 0.8 (IQR 0.62–2.1); p <0.05. In stage III NEC, monocyte counts decreased from median 2.1 × 10(9)/L (IQR 0.1.5–3.2) to 0.8 (IQR 0.6–1.9); p <0.05. There was no change in AMC in control infants. ROC of AMC values showed a diagnostic accuracy (area under the curve) of 0.76. In a given infant with feeding intolerance, a drop in AMC of >20% indicated NEC with sensitivity of 0.70 (95% CI 0.57–0.81) and specificity of 0.71 (95% CI 0.64–0.77). CONCLUSIONS: We have identified a fall in blood monocyte concentration as a novel biomarker for NEC in VLBW infants.