信号强度指数在传染病自动预警中的应用及评价

Application and evaluation of signal strength indictor in communicable disease automatic early warning system

目的为改进国家传染病自动预警系统（CIDARS），研究引入预警信号强度指数（SSI），以评估SSI在改善预警信号灵敏度中的作用。方法采用随机数字表法抽取全国2007—2011年痢疾病例报告数据和2010～2011年的预警信号数据，并计算SSI和疑似事件预警信号关联比（ER）。分析SSI与ER的相关关系，并用多因素logistic回归分析法探索SSI对ER的影响。结果2010—2011年CIDARS共发出的9620个预警信号中，传染病暴发疑似事件信号数74条（0．77％）。SSI分级与ER之间有良好的相关性：疑似事件相关联的信号的SSI中位数为4．0，远高于非疑似事件相关联的信号（1．7）；随着SSI的增加，事件关联比增加（r=0．917），当SSI超过20时，事件关联比可以高达20；多因素logistic回归模型分析发现，SSI与疑似事件信号的0R（95％CI）值为2．52（2．04～3．12）；流行季SSI对疑似事件概率的指示作用高于非流行季。结论SSI与ER的相关性很好，尤其是对于暴发规模相对较大的传染病暴发事件，且流行季的作用较非流行季明显。

Objective To explore the effect of signal strength indictor （SSI） in improving sensitivity of China Infectious Diseases Automated-alert and Response System （CIDARS）. Methods Diarrhea cases in 2007-2011 and early warning signals in 2010-2011 were selected by using random digital table method. Then, SSI and event-related ratio （ER） were calculated. The relationship between ER and SSI was analyzed, and the effect of SSI on ER was explored by using multiple logistic regression analysis. Results 9 620 early warning signals in 2010-2011 were generated in two years. Of these, 74, or 0.77% were defined as suspected outbreak signal The median of SSI related with suspected outbreak signal was 4.0, which was much higher than non-suspected outbreak signal （1.7）. ER was significantly correlated with SSI （r=0.917）. SSI classification has a good correlation between the ER, ER exceeded 20 after SSI reached 20. The multivariate logistic regression analysis showed OR of SSI related with suspected outbreak signal was 2.52 （95%CI 2.04- 3.12）. Compared with non-epidemic season, the relationship of SSI and ER in epidemic season was much higher. Conclusion SSI was closely related with ER. The relationship was much closer in large scale outbreak and epidemic season, and compared to non-epidemic,the effect of epidemic season is more obvious.