Abstract: Objective To study the predictive value of serum pentraxin 3 (PTX3) and copeptin in prognosis of children with severe pneumonia. 
Methods A total of 100 children with severe pneumonia admitted to our hospital were selected. According to the prognosis of children at 6-month follow-up, they were divided into poor prognosis group (n=35) and good prognosis group (n=65). After admission, the basic information of the children, including gender, age, blood and urine routine and course of disease, were recorded routinely, and targeted oxygen inhalation, anti-infection treatment and symptomatic support treatment were given. The disease severity and complications of the children were collected. After entering the pediatric Intensive Care Unit (PICU), the heart rate, respiratory rate, pH value, arterial oxygen partial pressure, blood potassium, urea nitrogen/serum creatinine, blood sodium, and hemoglobin were monitored for 24 h, and pediatric critical illness score (PCIS) was performed according to the measured results of the children. The serum copeptin level and PTX3 level were measured by enzyme-linked immunosorbent assay (ELISA) within 24 h after admission to NICU. Univariate analysis and multivariate Logistic regression analysis of the prognosis of children with severe pneumonia were compared, and receiver operating characteristic (ROC) curve was used to evalute the predictive value of combined determination of serum PTX3 and copeptin in prognosis of children with severe pneumonia. 
Results There was no significant difference in gender, the proportion of children with heart failure, average age, respiratory rate and heart rate between two groups (P＞0.05). There were statistically significant differences between two groups in PCIS score, numbers of patients with critical disease, serum PTX3 and copeptin levels (P＜0.05). According to the results of univariate analysis, the factors that had significant influence on the prognosis of children with severe pneumonia were included in multivariate analysis. The results showed that PCIS score, serum PTX3 and copeptin levels were independent influencing factors for the prognosis of children with severe pneumonia. The are under the ROC curve (AUC) of PTX3 were 0.861 (95%CI： 0.804-0.911, P＜0.001), the sensitivity was 71.12% and the specificity was 62.32%. The AUC of the serum copeptin was 0.841 (95%CI： 0.801-0.900, P＜0.001), with a sensitivity of 69.43% and a specificity of 65.21%. The AUC of the combined determination was 0.888 (95%CI： 0.853-0.943, P＜0.001), with a sensitivity of 78.66% and a specificity of 69.66%, suggesting that the combined determination of serum PTX3 and copeptin had certain predictive value for the prognosis of children with severe pneumonia, suggesting that the combined determination of serum PTX3 and copeptin had certain predictive value for the prognosis of children with severe pneumonia. 
Conclusion The combined determination of serum PTX3 and copeptin has a good predictive value for the prognosis of children with severe pneumonia.

Key words: pneumonia, pentraxin 3, copeptin