Performance efficiency of temporal model in China Infectious Diseases Automated-Alert and Response System in Gansu province, 2008-2013

Objective To analyze the performance efficiency of temporal model in China Infectious Diseases Automated-Alert and Response System(CIDARS)in Gansu province from 2008 to 2013 and to evaluate the sensitivity and practicability of CIDARS.Methods Data on infectious disease automated alert signals form CIDARS in Gansu province from January 2008 through December 2013 were collected and analyzed with descriptive methods and the effect of alert threshold adjustment in temporal model in CIDARS was assessed for different areas and diseases.Results Totally 39 940 early-warning signals were issued by CIDARS;the ratio between the number of reported infectious disease cases and the number of early-warning signals was 9.01:1;the suspected incident signals accounted for 1.57% of all the early-warning signals;the positive rate of early-warning signals was 0.64%.The majority of the warning signals were the incidents of dysentery,other infectious diarrhea,and mumps,accounting for 63.17% of all the warning signals.The early-warning signals involved 86 counties or districts of 14 prefectures in the province and the median response time for the signals was 0.84 hour.After the adjustment of early-warning threshold in December 2010,the sensitivity of CIDARS dropped from 70.59% to 39.62% and the positive rate dropped from 0.88% to 0.34%.The positive rate declined for the early-warning signals of influenza,mumps,rubella,hand foot and mouth disease,other infectious diarrhea,dysentery,hepatitis A,and acute hemorrhagic conjunctivitis;whereas the positive rate increased for the signals for the incidents in Lanzhou and Jiayuguan municipality.The median response time shortened for all the early-warning signals.Conclusion The performance of CIDARS in Gansu province was stable between 2008 and 2013,but the adjustment of early-warning threshold in CIDARS showed no good results,suggesting that the threshold still needs to be optimized for the improvement of sensitivity and specificity of CIDARS.