Abstract: Objective  To investigate the prognosticative value of neutrophil to lymphocyte ratio (NLR) and platelet (PLT) combined with D-dimer (D-D) in children with severe pneumonia complicated with sepsis.  Methods  The clinical data of 310 children with severe pneumonia complicated with sepsis admitted to the emergency intensive care unit (EICU) of Beijing Children's Hospital, Capital Medical University from January 2018 to January 2023 were reviewed. All the children were followed up by outpatient review or telephone after discharge, and the prognosis of the children was evaluated according to relevant criteria. They were divided into good prognosis group (n=198) and bad prognosis group (n=112). The hospital electronic medical record information system was used to collect the basic clinical data such as age and gender of all the children, record the early warning score ［chronic health status score Ⅱ (APACHEⅡ) and sequential organ failure assessment (SOFA) ］ of the children at admission, and collect the laboratory indicators within 24 h of diagnosis of sepsis. Logistic regression was used to analyze the related influencing factors of poor prognosis in children with pneumonia complicated with sepsis, and receiver operating curve (ROC) was used to analyze the sensitivity, specificity and accuracy of NLR, PLT count and D-D in predicting the prognosis of children with severe pneumonia complicated with sepsis.  Results  There was no significant difference in age and gender between the two groups  (P<0.05). APACHEII and SOFA scores in the poor prognosis group were significantly higher than those in the good prognosis group (P<0.05). The levels of NLR and D-D in the good prognosis group were significantly lower than those in the poor prognosis group, and the expression level of PLT was higher than that in the poor prognosis group (P<0.05). The variables with P ≤0.05 in univariate analysis were included in multivariate Logistic regression to determine the independent risk factors for prognosis. Adjusted for confounding factors such as age, sex, APACHE II score, and continuous variables, NLR and d-dimer levels were protective factors for prognosis （OR<1，P<0.05）, the expression level of PLT was a risk factor for prognosis（OR>1，P<0.05）. The results of ROC curve analysis showed that the area under the curve (AUC), sensitivity, specificity and accuracy were 0.949, 94.95%, 82.14% and 90.32%, respectively.  Conclusions  The NLR, PLT count and D-D in peripheral blood of children with severe pneumonia complicated with sepsis are significantly increased, and the three combined tests are of great value in predicting the prognosis of children.

Key words: neutrophil to lymphocyte ratio,  , platelet count, D-dimer, severe pneumonia complicated with sepsis, children, predictive value