Leukocytosis in very low birth weight neonates: Associated clinical factors and neonatal outcomes

Objective: Primary objective was to identify clinical factors and outcomes associated with leukocytosis in very low birth weight (VLBW) neonates. Secondary objective was to compare outcomes between infants with early-onset (≤72h of age) and late-onset leukocytosis (>72h). Study Design: A retrospective matched cohort study of VLBW neonates born at ≤30 weeks of gestation identified with a white blood cell count of ≥40000 was undertaken. Matched infants had no leukocytosis and were of similar gestational age. Data on common neonatal morbidities were collected from charts. Result: Leukocytosis was identified in 96 infants giving an incidence rate of 6.1%. Of all, 94 matched infants without leukocytosis were identified. There were no differences in the demographic features and risk factors between the two groups. The incidence of confirmed infection among infants with leukocytosis was 22%. No differences in common neonatal morbidities and mortality were identified between two groups. Late-onset leukocytosis (≥72h of age) was associated with sepsis and necrotizing enterocolitis. No differences in any of the other outcomes between early-onset and late-onset leukocytosis were identified. Conclusion: Leukocytosis, especially late onset, was associated with infection in VLBW infants. Late-onset leukocytosis was also associated with necrotizing enterocolitis indicating that postnatal age at time of leukocytosis should be considered when formulating clinical decisions.