Umbilical cord levels of interleukin-1 receptor antagonist and neonatal outcome.

Background: Previous studies indicate that there may be infant gender differences in cytokine expression associated with differences in neonatal morbidity.

Objective: We tested the hypothesis that umbilical cord interleukin-1 receptor antagonist (IL-1ra) correlates with infant gender and neonatal outcome in preterm infants.

Study design: IL-1ra was measured in cord blood taken from 58 preterm infants (33 males, 25 females) with gestational age less than 32 weeks. Receiver operating characteristics (ROC) curve were used for identifying IL-1ra values with high sensitivity and specificity for neonatal morbidity and adverse outcome, i.e., death or survival with severe intraventricular hemorrhage or periventricular leukomalacia.

Results: In the female infants, but not the male infants, cord IL-1ra values correlated with postnatal depression, expressed as Apgar scores at 1 min (correlation coefficient, r(s); p value: -0.542; 0.005), 5 min (-0.571; 0.018), and 10 min (-0.442; 0.035); and postnatal age at intubation (-0.799; 0.001). The ROC area under the curve (AUC) was 0.735 for adverse outcome (p=0.013), and 0.683 for bronchopulmonary dysplasia (p=0.021) when all infants were included. However, there was a significant gender difference in the ROC curve for adverse outcome (p=0.026), with AUC 0.640 (p=0.240) in males and AUC 0.929 (p=0.008) in females. Above a chosen cutoff at 13,500 ng/l for IL-1ra cord the sensitivity and specificity for predicting adverse outcome was 100 and 81%, respectively in females versus 50 and 84% in males.

Conclusion: Increased levels of cord IL-1ra levels are associated with neonatal morbidity and adverse outcome in preterm infants. Comparable levels of IL-1ra have different predictive value depending on infant gender.