Congenital heart diseases (CHD) are the most common causes of birth defects that have increased the risk of infections. Neonatal sepsis is a life-threatening condition and early diagnosis can be life-saving. We aimed to evaluate the potential role of the systemic immune-inflammatory index in the early diagnosis of neonatal sepsis.

A retrospective cohort study was conducted on 166 newborns with a diagnosis of neonatal sepsis who were admitted to our hospital with CHD between January 2017 and June 2021. Haematological indices including neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, and systemic immune-inflammatory index were calculated for all patients at the time of diagnosis of neonatal sepsis (sepsis). The sepsis values of these indices were compared with the admission values (pre-sepsis) of the patients.

The mean gestational age and birth weight of the patients were 38.36 ± 1.42 weeks and 3057.75 ± 484.68 g. It was found that absolute neutrophil count, systemic immune-inflammatory index, neutrophil/lymphocyte ratio, but not platelet/lymphocyte ratio were significantly increased at the time of sepsis. The receiver operating characteristic curve showed that systemic immune-inflammatory index, neutrophil/lymphocyte ratio, and absolute neutrophil count have predictive ability to define neonatal sepsis among newborns with CHD. The systemic immune-inflammatory index produced an area under the curve receiver operating characteristic curve of 0.76 (70% sensitivity, 70.5% specificity). To discriminate neonatal sepsis, the cut-off values of systemic immune-inflammatory index, neutrophil/lymphocyte ratio, and absolute neutrophil count were 517.19, 2.62, and 9210/mm3, respectively.

As an easily accessible and reliable indicator, systemic immune-inflammatory index may be used in combination with the other parameters in the early diagnosis of neonatal sepsis.