Objective To investigate correlation between the expression level of multiple cytokine levels in neonatal umbilical cord plasma and early-onset sepsis for screening out the cytokines with good diagnostic value for early-onset neonatal sepsis(EONS).Methods Full-term neonates and preterm neonates(Gestational age ≥ 32 weeks)of 310 cases between September 2021 and June 2023 were selected as study subjects.According to clinical signs,laboratory results and blood culture,these subjects were divided into 3 groups:control group without sepsis,EONS blood culture positive group and EONS blood culture negative group.Umbilical cord blood plasma of all subjects was collected within 72 hours after birth.The expression levels of cytokines IL-2,IL-4,IL-6,IL-9,IL-10,IL-21,IFN-γ and TNF-α were determined,and cytokines with high expression levels(high correlation)were screened out.Receiver operating characteristic(ROC)curve was used to analyze the specificity and sensitivity of the selected cytokines in the diagnosis of neonatal early-onset sepsis.Results Among the 8 cytokines mentioned above,the concentrations of IL-6,IL-9 and IL-21 in cord blood plasma of neonatal early-onset sepsis positive blood culture patients(392.6±258.7pg/ml,11.9±7.5pg/ml,29.1±16.8 pg/ml)and negative blood culture patients(353.8±244.5pg/ml,10.4±6.3pg/ml,27.7±19.2pg/ml)were higher than those of the control group(34.9±25.1pg/ml,5.9±4.5pg/ml,10.8±10.1 pg/ml),with significant differences(t=23.961,20.732;15.174,17.824;22.466,21.193,all P＜0.01),and the increase of IL-6 concentration was the most obvious.ROC curve analysis(the cut-off values of IL-6,IL-9 and IL-21:123.0 pg/ml,3.60 pg/ml,6.00 pg/ml,respectively)showed that the areas under the ROC curve for IL-6,IL-9 and IL-21 alone detection were 0.876(95％CI:0.786～0.955),0.782(95％CI:0.667～0.875)and 0.825(95％CI:0.737～0.913),respectively.The area under the ROC curve for the combined detection of IL-6,IL-9 and IL-21 was 0.930(95％CI:0.875～0.997).The combined detection of IL-6,IL-9 and IL-21 improved the specificity and sensitivity of the test than IL-6,IL-9 and IL-21 alone detection,and the differences were statistically significant(Z=2.137,2.391,2.257,all P＜0.05).There was no significant difference in cytokine expression between positive blood culture and negative blood culture neonates with early-onset sepsis(t=0.276～3.377,all P＞0.05).Conclusion The cytokines expression of IL-6,IL-9 and IL-21 in neonatal umbilical cord plasma of neonatal early-onset sepsis were increased.Combined detection of IL-6,IL-9 and IL-21 has good diagnostic value for early-onset neonatal sepsis.