Intrapartum chorioamnionitis is a common condition that often is managed by treating neonates with antibiotics. The Centers for Disease Control and Prevention recommends that children born to mothers with suspected chorioamnionitis receive a full diagnostic workup, including a complete blood cell count (CBC). A CBC test includes the absolute total neutrophil count (ATN), the total immature neutrophil count (ATI), and the ATI:ATN ratio (I:T). Jackson and colleagues studied whether neutrophil counts based on serial CBC tests aid in identifying at-risk neonates and what effect they might have on duration of antibiotic treatment and hospitalization, including costs. CBC tests are performed routinely at the onset of suspected chorioamnionitis.

New mothers with suspected chorioamnionitis were identified, and their newborns were evaluated after admission to the nursery. The authors performed blood cultures and measured CBCs at birth, at hour 12, and at hour 24. Neonates were divided into two groups—asymptomatic and symptomatic (i.e., showed respiratory distress or other clinical signs). All children received a 48-hour antibiotic regimen until blood cultures were negative. The symptomatic group and neonates with positive blood cultures were treated with intravenous antibiotics for four to seven days. Asymptomatic neonates with abnormal I:T values and a convenience sample of babies with normal I:T values received follow-up evaluation after discharge. The authors evaluated distribution of serial neutrophil counts in both groups and performed a cost assessment.

The study included serial CBC tests for 856 neonates. The symptomatic neonates were more likely to have abnormal I:T values compared with asymptomatic neonates, but the groups showed no significant differences in the other neutrophil values. At least one abnormal neutrophil value was observed in 97 percent of symptomatic neonates compared with 99 percent of asymptomatic neonates. Four or more abnormal values were observed in 64 percent of symptomatic neonates compared with 42 percent of asymptomatic neonates. Two thirds of I:T values were abnormal in 36 percent of symptomatic babies compared with 9 percent of asymptomatic babies. However, when only the second and third CBC tests were analyzed, 89 percent of symptomatic neonates and 79 percent of asymptomatic neonates had at least one abnormal neutrophil value. Neutrophil values in any combination had a positive predictive value no greater than 42 percent. Two percent of the asymptomatic neonates in the follow-up group were rehospitalized, but no cases were related to sepsis.

The authors conclude that serial neutrophil values in asymptomatic, culture-negative neonates born to mothers with suspected chorioamnionitis provided no significant information that improved or refined management. Antibiotic treatment and 48-hour observation were sufficient in managing infection. Using neutrophil values to guide decision-making only increased costs and prolonged hospitalization and antibiotic therapy. The authors suggest that more aggressive treatment should be reserved for symptomatic neonates or those with positive blood cultures after 48 hours.