Abstract: Objective　To investigate the clinical significance of serum calcium-binding protein S100A12 for the severity of mycoplasma pneumoniae pneumonia (MPP) in children. Methods　A total of 100 cases of MPP admitted to the department of pediatrics of the third hospital of Nanchang were selected from January 2018 to June 2019. According to the severity of the disease, they were divided into mild MPP group (n=60) and severe MPP (SMPP, n=40) group. Twenty healthy children examined in our hospital during the same period were selected as the control group. Serum samples were collected.  White blood cell count (WBC), neutrophils (N%), lymphocytes (L) and C-reactive protein (CRP) levels were detected. Serum levels of calcium-binding protein S100A12 were detected by ELISA. The differences of S100A12 in the acute and recovery stages were compared between MPP group and SMPP group. The correlation between S100A12 and the severity of MPP wasanalyzed. The ROC curve was used to analyze the clinical value of S100A12 in predicting severe MPP. Results　compared with the control group, serum levels of S100A12 were significantly increased in the acute phase of MPP group and SMPP group (P＜0.01). The serum level of S100A12 in the acute phase was significantly higher in SMPP group than that of MPP group (P＜0.05). There were no significant differences in the serum levels of S100A12 in the recovery phase between MPP and SMPP groups and control group (P＞0.05). Correlation analysis showed that S100A12 was positively correlated with the severity of MPP (rs=0.824, P＜0.01). ROC curve analysis showed that the area under the curve of S100A12 was 0.916 (95%CI: 0.843-0.962), the optimal threshold was 827.64 μg/L, the sensitivity was 95.00% and the specificity was 83.33%. Conclusion　The elevated S100A12 level can predict the severity of MPP in children.

Key words: pneumonia, mycoplasma, S100A12 protein, area under curve, severity, clinical significance