Abstract and Introduction
Abstract
Objective: To investigate associations between early low neutrophil count from routine blood samples, white blood count (WBC), pregnancy complications and neonatal outcomes for very low birth weight infants (VLBW ≤1500 g) with gestational age <32 weeks.
Study Design: Information was abstracted on all infants admitted to level III neonatal intensive care units in Wisconsin 2003 to 2004. A total of 1002 VLBW neonates (78%) had differential and corrected total white counts within 2 h of birth. Data analyses included frequency tables, binary logistic, ordinal logistic and ordinary regression.
Result: Low neutrophil count (<1000 per μl) was strongly associated with low WBC, pregnancy complications and antenatal steroids. Low neutrophil count predicted bronchopulmonary dysplasia severity level (odds ratio, OR: 1.7, 95% confidence interval, CI: 1.1 to 2.7) and intraventricular hemorrhage grade (OR: 2.2, 95% CI: 1.3 to 3.8).
Conclusion: Early neutrophil counts may have multiple causes interfering with their routine use as an inflammatory marker. Nonetheless, low neutrophil count has consistent independent associations with outcomes.
Introduction
Experimental studies of lambs and monkeys as well as careful observational studies of selected very low birth weight (VLBW, ≤1500 g) human neonates, have shown that a low number of circulating neutrophils in peripheral blood shortly after birth can be a marker for inflammatory processes and a predictor of neonatal lung disease, including bronchopulmonary dysplasia. There are also indications that a low number of neutrophils may be predictive of other neonatal complications. The previous human study excluded neonates born following certain maternal complications and treatments such as pregnancy-induced hypertension and antenatal steroid therapy that are associated with inhibition or enhancement of neutrophil counts. These exclusions limit the applicability of the findings, especially as antenatal steroid therapy is now almost ubiquitous. In addition, the neutrophil count in the above studies was mapped by sampling cord and/or early blood in well-controlled or single hospital settings. It is therefore not clear whether information from routine differential white counts obtained on an unselected population of VLBW neonatal intensive care unit (NICU) admissions carry predictive value for future complications and outcomes.
The Newborn Lung project has assembled a database with extensive clinical information on all VLBW infants born and admitted to NICUs in Wisconsin during the entire calendar years 2003 and 2004, thus providing a large unselected cohort of VLBW infants experiencing a range of regular care. We analyze neutrophil counts in routine blood samples taken within 2 h of birth for the subgroup born at less than 32 weeks gestation. We hypothesized that: (1) both neutrophil and total white blood counts (WBCs) are associated with pregnancy complications and neonatal characteristics; (2) neutrophil count, but not total white count is associated with early disease severity, bronchopulmonary dysplasia (BPD) and intraventricular hemorrhage (IVH).