Potential Substitution of Cord Blood for Infant Blood in the Neonatal Sepsis Evaluation

Abstract

Background: Evaluation of sepsis accounts for one third of all nursery triage admissions. If umbilical cord blood could be accurately substituted for infant blood, it would spare infants the discomfort of an invasive procedure and save both time and resources. While awaiting 48-hour blood culture results, we decide on clinical management based on whether the white blood cell (WBC) immature to total (I:T) granulocyte ratio is ≧0.2. Objectives: Our goal was to assess the correlation of complete blood count (CBC), I:T ratio and blood culture results between umbilical cord and infant blood. Methods: We conducted a prospective cohort study comparing CBC/differential and blood culture results of paired samples of umbilical cord and infant blood from term newborns. Results: We sent 113 paired samples of cord and infant venous blood for CBC/differential and blood culture. All 113 umbilical cord and infant blood cultures were negative, yielding a false-positive blood culture rate of zero. For 92% of babies, both the cord and infant blood I:T ratio were <0.2 or both were ≧0.2. Cord and infant WBC, hematocrit and platelet counts were moderately to highly correlated. Conclusion: We conclude that cord blood can be safely substituted for infant blood in routine sepsis evaluations of asymptomatic, term infants based on both the low false-positive cord blood culture rate and the significant association between high I:T ratios in cord and infant blood.