Study On Evaluation Of Temporal-spatial Model For Infectious Diseases Outbreak Detection

BackgroundResurgence of infectious diseases, emerging infectious diseases and diseases caused by bioterrorism attacks require early detection of infectious disease outbreaks, which can timely trigger disease control and prevent, to reduce the hazards of communicable diseases.The report quality of infectious diseases surveillance has greatly been improved since 2004. In order to make full use of surveillance data resources and early detecting the spatial aggregation of cases, China CDC further studies the spatial-temporal model of early detection for infectious diseases outbreak. In April 21, a pilot project of spatial-temporal early detection model had been launched in 20 provinces of China. The effectiveness of model is urgently needed to analysis and evaluates, so as to provide a scientific basis and recommendations for revising and improving the technology.Objective1. Establishment evaluation methods and indicators for early detection technology of infectious disease.2. Through analysis data of spatial-temporal model in pilot study and user questionnaire, comprehensively evaluate the effect of model, so as to provide a scientific basis and recommendations for revising and improving the technology.Data and Methods1. Data collectionResearch collected results of spatial-temporal model, infectious disease surveillance data, related events in pilot areas, and technical material. 2. Establishment evaluation methodsThrough literature review, early warning data analysis and expert advice, research on the evaluation framework and indicators in order to establish evaluation guildline for early warning systems.3. Warning effect evaluationBy calculating evaluation indicator, such as timeliness, sensitivity, specificity, positive predictive value, and analysis of the capacity of space exploration, early warning percentile, and comparing with the temporal model for comprehensive evaluation of spatial-temporal model's effectivities.4. Users questionnaireCarry out user questionnaire in Pilot areas, analyse the user's evaluation of warning timeliness, sensitivity, false-positive rate and so on.Results and conclusions1. Pilot performanceMost of the pilot areas for early warning have timely responsed to the signals. The stability of early warning system has been greatly improved, but has yet to be further improved.2. Effectiveness of Spatio-temporal early warning model(1) Timeliness:the Spatio-temporal model has better timeliness than temporal model, in particular those events discovered by suveillance data analysis, and this technology can help to promote disease control agency to earlier detect outbreak.But for the events directly reported by medical institutions, schools and other units, timeliness need to be further improved.(2) The accuracy of early warningIn general, the accuracy of Spatio-temporal model is better than temporal model. Spatio-temporal model has high sensitivity and specificity. Spatio-temporal model is superior to the positive predictive value of time model. Because of the events are rare, the positive predictive values of infectious diarrheal diseases, dysentery, hepatitis C are still low. Further studies need to be carried out for evaluating the effects of separate different types of disease and parameters.(3) Ability of detecting spatial aggregationThe cluster areas of cases detected by Spatio-temporal model have high coherence with the actual incidence of events. The geographic imformation of Space exploration is helpful for signal analysis.(4) Analysis of early warning percentilethe first signals of all event detected by Spatio-temporal model are above P50.Therefore, it is not necessary to detect the cluster below P50, which will not improve the detection sensitivity and timeliness of early warning.(5) Continious warning analysisCurrent exclusion method for continious early warning signals has played an important role, but there are still a large proportion of repeat signals, exclusion method must be further improved in programs to reduce the number of warning signals.3. Evaluation framework of early warning systems.Through using in evaluation of pilot results, the evaluation framework is feasible. The evaluation results are consistent with the user questionair results, which provids scientific evidences and advice for model and system improvement in next step of the research.Above all, after the pilot running of Spatio-temporal model has better effectiveness than temporal model, which has a good early warning timeliness, accuracy and capacity of space exploration. Spatio-temporal model will be helpful for disease control agencies to abnormal data analysis for detecting epidemic and outbreak. It can be used in disease control agencies of all levels in China, after improving the model and paraments.