现场流行病学的基石病例定义.ppt

现场流行病学的基石 ——病例定义;主要内容Contents;为什么使用病例定义? Why use a case definition?;疾病监测的病例定义必须始终保持一致Case definitions for surveillance need to be consistent over time.;2005－2006年某社区病毒性肝炎每周报告发病率Viral Hepatitis by week for one county, 2005-2006 ;2005－2006年某社区剔除社区医院的病毒性肝炎每周报告发病率Viral Hepatitis for a county with and without one hospital, 2005-2006;病例的错误分类可导致流行病学分析偏差Misclassified cases can bias epidemiologic analysis;完美的病例分类则可给出不同的率Perfect classification gives different rates;在消灭某种疾病X的过程中与其相似疾病的发病率等于10During elimination of disease X the incidence of similar disease = 10;在消灭某种疾病X的过程中与其相似疾病的发病率等于1During elimination of disease X the incidence of similar disease = 1;什么是病例定义? What is a case definition? ;不同专家会对同一（群）病人进行相同分类吗？Will experts classify the same patients the same?;是否可能存在完美专家？Will one expert be perfect?;一个典型的病例定义（临床诊断）：麻疹A typical case definition: measles;敏感度和特异度Sensitivity and specificity;病例定义永远不可能完美Case definitions are never perfect;敏感度等于真实病例被准确判定的比例Sensitivity = proportion of true cases correctly identified;特异度等于非病例被准确判定的比例Specificity = the proportion of non-cases correctly identified;假定某社区在疾病X暴发期间同时存在其它不同疾病Consider a county with different diseases during an outbreak of Disease X. ;高度敏感的病例定义必将包括很多其它疾病的病例A case definition that includes all cases will include many other diseases ;高度特异的病例定义必将排除包括很多真实病例A case definition that includes only cases will exclude many cases ;病例定义可有多个水平The case definition may have levels of certainty. ;细菌性痢疾暴发的病例定义Case definition for a shigellosis outbreak;敏感度和特异度可随目标的不同而变化Variability in sensitivity and specificity depends on purpose;暴发期间使用敏感病例定义During outbreaks the performance of a sensitive case definition improves;构建病例定义Construction of case definitions;疾病识别标志：Disease Identifiers: ;流行病学标准Epidemiologic criteria;感染性胃肠炎：病例定义示例Infectious gastroenteritis: Example case definition;使用一个大多数或全部病例具有的症状特征Use one characteristic that will include most or all cases;使用在某些病例中发现的更具特异性的症状特征Use more specific characteristics that are seen in s