Abstract: Objective To study the changes and correlation of serum high mobility group protein B1(HMGB1), granulocyte-macrophage colony-stimulating factor(GM-CSF) and lactate dehydrogenase(LDH) in children with chronic pneumonia, so as to provide reference for the diagnosis and treatment of the disease. 
Methods A total of 66 children with chronic pneumonia were selected as the pneumonia group, and another 80 healthy children were selected as the control group. The serum HMGB1, GM-CSF and LDH levels of the two groups were detected and compared. Children in the pneumonia group were divided into the severe pneumonia group and the mild pneumonia group according to the severity of the disease, and the levels of HMGB1, GM-CSF and LDH were compared between two groups. The relationship between serum HMGB1, GM-CSF and LDH in the pneumonia group was analyzed by Pearson correlation analysis. The receiver operating characteristic(ROC) curve was used to evaluate the value of serum HMGB1, GM-CSF and LDH in assessing the severity of children with chronic pneumonia. 
Results The levels of serum HMGB1, GM-CSF and LDH in the pneumonia group were higher than those in the control group, and the difference was statistically significant(P＜0.001). The levels of serum HMGB1, GM-CSF and LDH in the severe pneumonia group were higher than those in the mild pneumonia group, and the difference was statistically significant(P＜0.001). Pearson correlation analysis showed that serum HMGB1 was positively correlated with GM-CSF and LDH levels(r=0.340, 0.508)(P＜0.05), and LDH was positively correlated with GM-CSF level(r=0.553)(P＜0.05). ROC results showed that cut-off value of HMGB1, GM-CSF and LDH was 11.26 μg/mL, 116.89 μg/mL and 335.41 U/L, respectively. The area under the ROC curve(AUC) of HMGB1, GM-CSF and LDH in evaluating chronic severe pneumonia was 0.790, 0.787 and 0.781, respectively, and the AUC of the combination of the three was 0.906. The AUC of combined evaluation was higher than that of single indicator, and the difference was statistically significant(P＜0.05). 
Conclusion The increased levels of HMGB1, GM-CSF and LDH in peripheral blood are related to the occurrence and development of chronic pneumonia in children, and the levels of the three are positively correlated with each other in children with chronic pneumonia. The combined detection has good efficacy for disease assessment.

Key words: pneumonia, lactate dehydrogenase, children