Objective. Early recognition is important for the successful treatment and outcome of neonatal infections. As interleukin-6 (Il-6) plays a critical role in the induction of C-reactive protein (CRP) synthesis in the liver, it was hypothesized that this cytokine could be detected earlier in blood than the CRP during the course of bacterial infection.

Design. In a prospective study of 298 newborns who were admitted to the nursery unit, CRP levels, blood cell count with differential, and Il-6 levels were determined at the time of admission and 24 hours after admission. Seventy-six newborns were excluded from the study because of incomplete or incorrect blood sampling.

Results. The remaining 222 newborns were assigned to one of five groups: 11 newborns with blood culture-positive sepsis (sensitivity of Il-6 on admission 73%), 15 newborns with clinical sepsis (sensitivity of Il-6 on admission 87%), 41 newborns with infection (sensitivity of Il-6 on admission 68%), and 54 newborns without clinical and laboratory evidence of infection (specificity 78%). The remaining 101 newborns were defined as a mixed group because the diagnosis of neonatal infection could not clearly be made. Seventy-five percent of infected newborns had negative Il-6 levels 24 hours after admission. Of the 18 infected newborns with negative Il-6 levels on admission, 10 newborns had elevated CRP levels, suggesting that Il-6 was already negative because of the short half-life of Il-6. Sensitivity of Il-6 in CRP-negative newborns on admission was 100% in newborns with blood culture-positive and clinical sepsis. Il-6 was more sensitive than CRP in infected newborns on admission (73% vs 58%).

Conclusion. Il-6 is a sensitive parameter for diagnosing neonatal bacterial infection. The combination of CRP and Il-6 seems to be the ideal tool for the early diagnosis of neonatal infection.

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