现场流行病学的基石病例定义知识

1、现场流行病学的基石病例定义知识主要内容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 illness为什么使用病例定义? Why use a case definition

2、?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 activities地区间的比较 Compare areas比较结果应真实反应疾病本身的

3、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 year20052006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 乙肝HBV未分型肝炎Unspecified hepatitis20052006年某社

4、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暴露Exposed病例 Cases非病例Not Cases合计Total真实True相似疾病Similar disease小计Total是 Yes 80201009001000否 No2020409601000合计Total1004014018602000

5、暴露组发病率 Rate in exposed 10%未暴露组发病率 Rate in unexposed4%相对危险 Risk ratio（RR）2.5危险差异 Risk difference 6%完美的病例分类则可给出不同的率Perfect classification gives different rates暴露Exposed病例Cases非病例Not Cases合计Total真实病例True相似疾病Similar disease合计Total是 Yes 800809201000否 No200209801000合计Total100010019002000暴露组发病率 Rate in exp

6、osed 8%10%未暴露组发病率 Rate in unexposed2%4%相对危险度 Risk ratio（RR）4.02.5危险差异 Risk difference 6%6%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相似疾病Similar disease疾病XDisease 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1During elimination of disease

7、 X the incidence of similar disease = 1监测到的病例总数Total disease detected疾病XDisease X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 V

8、aries 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 patients 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? C

9、ase 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

10、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 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Sensitiv

11、ity and specificity敏感度 Sensitivity 能够发现的病例占所有真实病例的比例 of all 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 a

12、re never perfect按病例定义判定By Case definition真实病例True Cases合计Total是 Yes否 No病例 Cases9020110非病例 Not cases108090合计 Total100100200敏感度等于真实病例被准确判定的比例Sensitivity = proportion of true cases correctly identified按病例定义判定 By Case definition真实病例True Cases合计Total是 Yes否 No病例 Cases9020110非病例 Not cases108090合计 Total1001

13、00200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按病例定义判定真实病例 True Cases合计TotalBy Case definition是 Yes否 No病例 Cases9020110非病例 Not cases108090合计 Total100100200特异度 Specificity = 80/

14、100 = 0.80 = 80%假阳性率 Percentage false positives = 20/100 = 0.20 = 20%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Otherdiseases疾病XDisease 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 inclu

15、de many other diseases 高度敏感的病例定义This is called a “highly sensitive” case definition非病例NotCases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NotCases病例定义可有多个水平The case definition may

16、have levels of certainty. 非病例NotCases疑似病例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NotCases腹泻Diarrhea 2 daysDiarrhea 2 days+呕吐Vomit 或者OR 发烧Fever 38CDiarrhea 2 days+Vomit 并且AND Fever 38CSuspect, orPossible, orPro

17、bable+实验室阳性Shigella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 reg

18、istries内部或者外部使用 For internal or external use暴发期间使用敏感病例定义During outbreaks the performance of a sensitive case definition improves相似疾病暴发疾病疾病暴发构建病例定义Construction of case definitions疾病识别标志：Disease Identifiers: 症状 Symptomatology体征（物理检查） Signs (Physical examination)临床评价 Clinical evaluations (EKG, EEG, etc

19、.)不符合其他疾病 Lack of compatibility with other diseases治疗情况 Response to treatment实验室检测（病毒分离、血糖等） Laboratory tests (virus isolation, blood sugar, etc.)流行病学标准Epidemiologic criteria时间 Time地点 Place人 Person宿主因素（基础疾病） Host factors (underlying illness)与其它病例的流行病学联系 Linkages to other cases相关危险因素 Associations wit

20、h risk factors感染性胃肠炎：病例定义示例Infectious gastroenteritis: Exle case definition临床 Clinical:腹泻（3次以上稀便x2天） Diarrhea (3+ liquid stools x 2 days) 发热 Fever无其他原因（药物抗生素） No other cause (drugs - antibiotics) 实验室确诊 Confirmed Laboratory:粪便中发现病原体 Organism identified in stool流行病学 Epidemiological在最短潜伏期内住院 Hospitaliz

21、ed for minimum incubation period潜伏期期间在医院 In hospital during incubation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腹泻 Diarrhea发热 Fever黄疸 Jaundice出疹 Rash出疹并发热 Rash+fever咳嗽并发热 Cough + fever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 some case

22、s特殊发现 Specific findings杨梅舌猩红热 Strawberry tongue - scarlet fever特殊病症 Pathognomonic finding柯氏斑麻疹 Koplicks spots = measles使用一组一般性的症状特征Use a group of common findings卡他症状 Coryza咳嗽 Cough结膜炎 Conjunctivitis其它标准Other criteria不能被其它已知疾病所能解释的症状 Symptoms not explained by another confirmed disease or condition既往健

23、康人所具有的特征 In a previously healthy person川崎病Kawasaki disease发热持续5天或以上 Febrile illness for 5 or more days并同时具有以下5种症状中的4种 With four of the following five findings双眼结膜充血 Bilateral conjunctival injection新发口腔粘膜破损 Oral lesions (new)手指和脚趾破损 Lesions on fingers and toes皮疹 Skin rash颈部淋巴结病 Cervical lymphadenopat

24、hy新生儿破伤风Neonatal Tetanus新生儿 Neonate who 出生时啼哭 Cried at birth出生后头两天内能正常吸允 Had normal suck for first 2 days of life出生后第3天至30天以内 Developed from 3 to 30 days after birth无力吸允 Inability to suck出现痉挛 Generalized spasticity可有惊厥 With or without convulsions死亡 Commonly results in death百日咳Pertussis咳嗽并具有以下任一特征 Co

25、ugh with one of the following characteristics咳嗽持续2周或2周以上 Continues for 2 or more weeks阵发 With paroxysms咳嗽后呕吐 Posttussive vomiting病例定义应用实例Applying case definitions举例：人狂犬病监测病例定义的标准Exle criteria for a case definition for human rabies for surveillance临床标准 Clinical:脑炎 Encephalitis发病后10天内死亡 Death within 1

26、0 days of onset实验室标准 Laboratory:头发毛囊、角膜或者脑组织免疫荧光抗体染色阳性 Direct FA of hair follicle, cornea or brain抗狂犬病毒IgG或IgM抗体阳性（未经免疫者） Anti-rabies IgG or IgM in an unvaccinated person流行病学标准 Epidemiological:被已知宿主动物咬伤 Bite from a known reservoir animal species被患狂犬病的动物咬伤 Bite from a rabid animal 举例：狂犬病病例定义Exle rabi

27、es case definition疑似病例 Suspect患脑炎并于10天内死亡 Encephalitis with death in 10 days可能病例 = 疑似病例 Possible = suspect and 动物咬伤 animal bite临床诊断病例 = 疑似病例 Probable = suspect and被患狂犬病的动物咬伤 bite from rabid animal确诊病例 =疑似病例、可能病例或者临床诊断病例 Confirmed = suspect, possible or probable免疫荧光抗体检测狂犬病毒 阳性 Rabies virus by direct

28、FA from cornea, hair follicle, or brain或者抗狂犬病毒IgM抗体阳性（未经免疫者） Or anti-rabies IgM in an unvaccinated person根据以下报告的狂犬病例数据，哪些病例符合病例定义？Some data from reported rabies cases. Which fit the case definitions?E=脑炎encephalitisY = 是YesN = 否NoR =患狂犬病的动物 Rabid AnimalO= 其它动物 other animalND =没有检测 Not doneCI = 角膜印迹C

29、orneal ImpressionBr = 脑组织 Brain腮腺炎性脑膜脑炎Mumps meningoencephalitis临床标准 Clinical脑膜炎或脑炎症状并发热大于37.5度 Symptoms of meningitis or encephalitis with fever (37.5 C)脑脊液白细胞计数大于50个/ml、葡萄糖大于3,0 um/L CSF with 50 leucocytes/ml y glucose 3,0 um/L前2周内患有流行性腮腺炎 Mumps disease within 2 weeks before流行病学标准 Epidemiologic发病前

30、一个月与流行性腮腺炎患者面对面接触 过 Face-to-face contact with a mumps case in the month before onset实验室确诊 标准 Laboratory confirmation 抗腮腺炎病毒IgM抗体 Anti-mumps IgM 分离到腮腺炎病毒 Isolation of mumps virus流行性腮腺炎性脑膜炎Mumps Meningitis疑似病例 Suspect症状加接触 Symptoms plus contact可能病例 Possible症状加流行性腮腺炎 Symptoms plus mumps disease临床诊断病例 P

31、robable疑似或者可能病例加脑脊液检查 Suspect or possible with compatible CSF确诊病例 Confirmed上述三种病例 Suspect, possible or probable急性期或恢复期检测到IgM抗体或分离到腮腺炎病毒 Anti-mumps IgM or isolation of mumps virus during acute illness or convalescence根据以下病例一览表判定哪些病例符合病例定义Can you apply the case definition to this line-listing of patie

32、nts?病例一览表Exle of a Line Listing1=“Yes”?=“Dont know”0=“No”ID #发病日期Date of SymptomOnset症状 Signs/Symptoms实验室结果Labs人口统计学Demographics腹泻Diarrhea呕吐Vomit发热Fever 101Positive stool culture年龄Age性别Gender11/2/0411?119M21/5/04010017M31/2/04010123F41/7/04111118?51/1/04?11118F如何制作一览表How to Create a Line Listing及时添加新的确诊病例 Add new cases as they are identifie