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1、现场流行病学的基石 病例定义,刘 明 斌2010年2月25日,南昌市疾病预防控制中心 中国现场流行病学培训项目,主要内容 Contents,为什么要使用病例定义？Why use a case definition? 什么是病例定义？What is a case definition? 敏感度和特异度问题Sensitivity and specificity 构建病例定义Construction of case definitions 监测系统病例定义应用实例Applying case definitions 病例一览表Line Listing 疾病的时间序列Time sequence of i
2、llness,为什么使用病例定义? Why use a case definition?,医生、护士、实验室和其他人员依法报告Doctors, nurses, laboratories, and others report notifiable events 资料产生外在变异 Produces extraneous variability in these data 减少变异性以便：Need to minimize this variability to: 监视趋势Monitor trends 评价干预效果Evaluate the effectiveness of intervention a
3、ctivities 地区间的比较 Compare areas 比较结果应真实反应疾病本身的变化和不同 Comparisons must reflect changes or differences in the disease,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.,报告病例数 Reported Cases,年份 Quarter year,20052006年某社区病毒性肝炎每周报告发病率 Viral Hepatitis by week for one county,
4、 2005-2006,乙肝 HBV,未分型肝炎 Unspecified hepatitis,20052006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,剔除社区医院,社区总报告发病率,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
5、疾病X的过程中与其相似疾病的发病率等于10 During elimination of disease X the incidence of similar disease = 10,相似疾病 Similar disease,疾病X Disease X,监测到的疾病总数 Total disease detected,在消灭某种疾病X的过程中与其相似疾病的发病率等于1 During elimination of disease X the incidence of similar disease = 1,监测到的病例总数 Total disease detected,疾病X Disease X,
6、相似疾病 Similar disease,什么是病例定义? What is a case definition?,一套标准 A set of standard criteria 用于确定是否感染Used to decide if a person has an infection 保证卫生统计结果是真实可信的 Assures that differences in health statistics are real 根据目的不同而不同Varies with the purpose,不同专家会对同一（群）病人进行相同分类吗？ Will experts classify the same pat
7、ients the same?,10位专家会诊100位病人 10 experts review 100 patients 每位专家均将他们划分为某病病人或非病人 Each expert classifies them as a case or not a case of a disease X 每位专家会按同样方法对每位病人进行分类吗？Will every expert classify every patient the same way? Case or not a case?,是否可能存在完美专家？ Will one expert be perfect?,假设一位专家审阅100位病人的诊
8、疗记录 One expert reviews 100 patient records. 他将如何判定病人与非病人？ A case or not a case of a disease X? 一个月后同一专家重新审阅上述100位病人的诊疗记录又将如何？ One month later the expert reviews the same 100 records. 不同专家将会用同一方法或标准判定每位病人？Will every expert classify every patient the same way? Case or not a case?,一个典型的病例定义（临床诊断）：麻疹 A
9、typical case definition: measles,出皮疹37天 Generalized skin rash of 3 to 7 days duration 体温大于38度 Fever 38C 加上以下一项或多项 Plus one or more of the following 鼻卡他症状 coryza (鼻塞 stuffy, 流涕 runny nose) 咳嗽 cough 结膜充血 conjunctival injection,敏感度和特异度 Sensitivity and specificity,敏感度 Sensitivity 能够发现的病例占所有真实病例的比例 of al
10、l the true cases of the disease how many (what percent or proportion) does the method discover? 特异度 Specificity 能够发现的非病例占所有非病例的比例 of all the non-cases how many (what percent or proportion) does the method discover?,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 = propor
11、tion of true cases correctly identified,敏感度 Sensitivity = 90/100 = 0.90 = 90%,假阴性率Percentage false negatives = 10/100 = 0.10 = 10%,特异度等于非病例被准确判定的比例 Specificity = the proportion of non-cases correctly identified,特异度 Specificity = 80/100 = 0.80 = 80%,假阳性率 Percentage false positives = 20/100 = 0.20 = 2
12、0%,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.,与疾病X相似 Similarity to disease X,其它疾病 Other diseases,疾病X 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,高度敏感的病例定义 This is called a “highly
13、sensitive” case definition,非病例 Not Cases,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,X疾病病例 Disease X,高度特异的病例定义 This is called a “highly specific” case definition,非病例 Not Cases,病例定义可有多个水平 The case definition may have levels of certainty.,非病例 Not Cases,疑似病例
14、 Suspect,可能病例 Possible,临床病例 Probable,确诊病例 Confirmed,特异度 Specificity,敏感度 Sensitivity,细菌性痢疾暴发的病例定义 Case definition for a shigellosis outbreak,非病例 Not Cases,腹泻 Diarrhea 2 days,Diarrhea 2 days +呕吐Vomit 或者OR 发烧Fever 38C,Diarrhea 2 days +Vomit 并且AND Fever 38C,Suspect, or Possible, or Probable +实验室阳性Shigel
15、la,疑似病例 Suspect,可能病例 Possible,临床病例 Probable,确诊病例 Confirmed,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,诊断和治疗 Diagnosis and treatment of patients. 流行病学调查阶段 Phase of an epidemiologic investigation 确证暴发原因 To identify cause 常规监测或疾病登记 For routine surveillance or registries 内部或者外部使用 For internal or external use,
