Cord Blood Levels of Interleukin-6 and Interleukin-8 for the Immediate Diagnosis of Early-Onset Infection in Premature Infants

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Abstract
Background: Cytokine plasma levels are suggested to be sensitive indicators of neonatal sepsis, but conventional assays are time consuming. This study aimed at evaluating the significance of cord blood levels of interleukin (IL)-6 and IL-8 determined by a fully automated random access assay within 90 min of admission to predict systemic bacterial infection. Patients and Methods: Cord blood levels of IL-6 and IL-8 were determined in 71 mature and 100 premature infants by a chemiluminescence assay (Immulite®). Patients were divided into four groups according to a clinical and laboratory scoring system. Group A: documented early-onset infection; group B: infection possible; group C: infection unlikely, and group D: healthy newborns. Results: Median IL-6 levels in the subgroup of premature newborns were as follows: group A, 1,920 pg/ml (5–95% confidence interval 308–4,660 pg/ml); group B, 50 (15–102) pg/ml; group C, 21 (12–71) pg/ml, and group D, 8 (6–11) pg/ml. For IL-8, median levels for groups A–D were 289 (226–514) pg/ml, 87 (40–107) pg/ml, 44 (33–98) pg/ml and 21 (16–25) pg/ml, respectively. The difference between group A and the other groups was highly significant (IL-6 p < 0.0001, IL-8 p < 0.001). At a cut-off of 80 pg/ml, the sensitivity of IL-6 for the diagnosis of sepsis was 96% (specificity 95%). For IL-8 (cut-off 90 pg/ml), the sensitivity was 87% (specificity 94%). Conclusion: In premature infants, the diagnosis of an early-onset infection can be established or ruled out with a high level of confidence by measuring IL-6 or IL-8 levels from cord blood using a random access chemiluminescence assay.