A Study On The Sensitivity Of Measles Cases And Outbreaks In China

BackgroundThe sensitivity of the monitoring system is an important indicator which reflects the authenticity of infectious disease surveillance data. The sensitivity of the monitoring system shows the representation and stability of the monitoring data, and also embodies the importance in the area of disease distribution description, infectious morbidity estimation and epidemic trend identification. Measles surveillance reinforcement is one of the key measures to eliminate measles which is recommended by World Health Organization, especially in the phase of measles elimination which demand high quality measles surveillance. China has established a measles surveillance system which is a combination of epidemiology and laboratory. So, evaluating the sensitivity of cases and the measles outbreak report is very significant for China to boost the measles surveillance quality.ObjectivesExplore ways to evaluate the sensitivity of surveillance system, evaluate the sensitivity of case and outbreak reports of Chinese measles surveillance system by the way of case report and outbreak detection ability, and provide scientific basis for perfecting measles surveillance system and upgrading the quality of measles surveillance.MethodsBy using the stratified sampling method,6provinces are selected as the study field which extracting from the eastern, central and western part of China. Then, seven hospitals in each province have been randomly selected, including two provincial hospitals, a municipal hospital, two county hospitals and two town hospitals. Finally,60measles cases have been randomly selected which was diagnosed from each hospital during the first half of2010. Retrospective investigation method was used to survey the report rate and the diagnosis accuracy. The measles discarded case report incidence of each province in2010was downloaded from the measles surveillance information system to evaluate whether the province has reached to the requirement of surveillance standard. According to the report standard of measles outbreak and public health emergency events, measles outbreaks and measles emergency events were identified from the cases which was from the disease surveillance information system in the year of2009and2010, and measles outbreak was also downloaded from the measles surveillance system and measles emergency events was identified, at the same time, the measles emergency events were downloaded from the public health emergency response management system. The measles outbreak and emergency events from the former3systems were matched and compared through the key variable manually to calculate the report sensitivity of measles outbreak.Results1. Report sensitivity of measles casesIn this study,751measles cases from42hospitals were collected. The average hospital report rate is98.40%, the sensitivity and positive predictive value of measles cases is99.40%and67.66%respectively. In accordance with the discarded measles cases have been revised completely in the measles surveillance system, so the actual positive predictive value of measles cases in measles surveillance system is100%. In2010, the national reported rate of discarded measles cases was1.39per100thousand; meanwhile the reported rate had reached2per100thousand in8provinces, and the reported rate of discarded measles cases among1077counties has reached more than1per100thousand which account for36.7%of the2929counties.2. Report sensitivity of measles outbreakAfter the analysis and match of data which are collected from the disease surveillance information management system and measles surveillance information management system, the estimated number of national measles outbreaks between the year of2009and2010was1632according to the national reporting standards,1557were detected through disease surveillance information management system, the sensitivity was95.40%.664were detected through measles surveillance information management system, the sensitivity was40.69%.After the analysis and match of data which are collected from the disease surveillance information management system, measles surveillance information management system and public health emergency response management system, the estimated number of national measles public health emergency events between2009-2010was10according to the national public health emergency response standard, but only9events were reported in the public health emergency response management system which including3unqualified events, so the sensitivity was60%.ConclusionsThe sensitivity of measles cases report in hospitals is quite high. But the reported rate of discarded measles cases in most provinces of china failed to meet the requirements of surveillance plan. Measles cases collected from disease surveillance information management system can be used to detect most of the measles outbreaks. But the sensitivity of measles outbreaks and public health emergency events report is quite low. Not all suspected measles cases were reported as surveillance subjects, because the doctor did not follow the’measles surveillance plan’when they diagnosing these cases, this is a major factor influencing the sensitivity of measles cases report. The major influencing factor for low measles outbreak report rate is due to the bad analysis and use of surveillance data among county CDC staff in their daily work, and they are also unfamiliar with the report standard.