Abstract: Objective To investigate the changes of serum Th1/Th2 cytokines in children with viral encephalitis (VE) complicated with myocardial injury and their diagnostic efficacy. 
Methods In total, 102 children with VE complicated with myocardial injury in our hospital were selected as the research group, and following the 1〖DK〗∶1 allocation principle, 102 patients with VE and 102 healthy children were included as control group and normal control group respectively. Serum Th1 cytokines ［interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α)］, Th2 cytokines ［interleukin (IL)-4, IL-10］, myocardial zymogram indicators ［lactate dehydrogenase (LDH), myocardial injury markers creatinine I (cTnI), and creatine kinase isoenzymes (CK-MB)］ were calculated in the three groups. The serum Th1/Th2 cytokines of different degrees of myocardial injury in the research group was compared, and Spearman was used to analyze the correlation between serum Th1/Th2 cytokines and the degree of myocardial injury. Receiver operating characteristic (ROC), decision curve analysis (DCA), and clinical impact curve (CIC) were drawn to analyze the diagnostic value of serum Th1/Th2 cytokines in VE combined with myocardial injury. 
Results The levels of serum IFN-γ, TNF-α, CK-MB, cTnI and LDH were the highest in the research group, followed by the control group and normal control group, and the levels of serum IL-4 and IL-10 were the lowest in the research group, followed by the control group and normal control group (P＜0.05). The levels of serum IFN-γ and TNF-α in the research group were the highest in those with severe myocardial injury, followed by those with moderate injury and those with mild injury, and the levels of serum IL-4 and IL-10 were the lowest in patients with severe myocardial injury, followed by those with moderate injury and those with mild injury (P＜0.05). In children with VE complicated with myocardial injury, the degree of myocardial injury was positively correlated with IFN-γ and TNF-α (r=0.599, 0.634) (all P＜0.05), and negatively correlated with IL-4 and IL-10 (r=-0.602, -0.587) (all P＜0.05). The area under the curve (AUC) of serum Th1/Th2 cytokines in combination and myocardial zymogram in combination in the diagnosis of VE complicated with myocardial injury was 0.928 (95%CI: 0.883-0.959) and 0.933 (95%CI: 0.890-0.963) respectively, showing similar diagnostic efficacy. DCA and CIC curves showed that the model combined with Th1 and Th2 cytokines in the diagnosis of VE combined with myocardial injury had higher net yield and clinical effective rate. 
Conclusion The serum Th1/Th2 cytokine level in children with VE complicated with myocardial injury is obviously abnormal, which is closely related to the degree of myocardial injury. The combination of IFN-γ, IL-10, TNF-α and IL-4 in combination in the diagnosis of VE complicated with myocardial injury has high diagnostic efficacy and clinical benefit. 

Key words: encephalitis, viral, myocardial injury, ROC curve