Objective Adjunctive tests are needed to predict sepsis in the newborn and to lower the rate or duration of unnecessary antibiotic use. We evaluated the normal Inter-⍺ inhibitor protein (IaIp) values in infants and the association of plasma levels of IaIp with sepsis in term and preterm newborns.

Methods Plasma IaIp levels were measured by enzyme-linked immunosorbent assay in samples from 135 newborn infants at a wide range of gestational ages (24–42 weeks). IaIp levels were also determined in 19 infants undergoing prospective evaluation for sepsis.

ResultsIaIp levels in umbilical cord blood and circulating peripheral blood of healthy newborn infants (525±66 mg/L) were not significantly different from the level in healthy adults (691±80 mg/L). IaIp levels were similar in infants between 24 and 42 weeks gestational age. There was a significant reduction in IaIp levels in infants with sepsis compared with nonseptic controls (169±126 mg/L vs 613±286 mg/L, P<.0001).

ConclusionsIaIp levels in the blood of newborns are independent of gestational age and similar to adults. IaIp levels are significantly reduced in infants with bacterial sepsis and might serve as an adjunctive diagnostic marker to allow prospective reduction of antibiotic use.