Abstract: Objective  To investigate the early predictive value of serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), procalcitonin (PCT),  interleukin-6 (IL-6) and D-dimer (D-D) in children with sepsis secondary to soft tissue infection. 
Methods  In total, 138 children with soft tissue infection admitted to the Department of Orthopedics were selected as the soft tissue infection group, and were divided into a common infection group (n=99) and a sepsis group (n=39) based on presence of secondary sepsis. Additionally, 68 normal children during the same period were selected as the control group, and all children were tested for CRP, ESR, PCT, IL-6, and D-D for comparison. 
Results  The levels of CRP, ESR, PCT, IL-6, and D-D in the soft tissue infection group were higher than those in the normal control group (P＜0.05). The levels of CRP, ESR, PCT, IL-6, and D-D in the common infection group were all lower than those in the sepsis group (P＜0.05). Logistic regression analysis showed that CRP≥35 mg/L, ESR ≥44 mm/1 h, PCT ≥0.08 g/L, IL-6 ≥11 pg/L, and D-D ≥0.72 mg/L were independent risk factors for soft tissue infection-induced sepsis in children. The receiver operating characteristic (ROC) curve analysis showed that the area under the ROC curve (AUC) values of CRP, ESR, PCT, IL-6, and D-D alone and in combination were 0.578, 0.680, 0.784, 0.881, 0.824, and 0.921, respectively. The AUC values of the combined detection of five indicators were greater than those of individual detection. 
Conclusion  The levels of CRP, ESR, PCT, IL-6 and D-D are significantly increased in children with soft tissue infection, which are independent risk factors of sepsis secondary to soft tissue infection. The combined detection of five indicators has higher value in prediction and diagnosis of secondary sepsis. 

Key words: soft tissue infection, sepsis, serological index