現(xiàn)場流行病學的基石病例定義知識

1、現(xiàn)場流行病學的基石病例定義知識主要內(nèi)容Contents為什么要使用病例定義？ Why use a case definition?什么是病例定義？ What is a case definition?敏感度和特異度問題 Sensitivity and specificity構(gòu)建病例定義 Construction of case definitions監(jiān)測系統(tǒng)病例定義應用實例 Applying case definitions病例一覽表 Line Listing疾病的時間序列 Time sequence of illness為什么使用病例定義? Why use a case definition

2、?醫(yī)生、護士、實驗室和其他人員依法報告 Doctors, nurses, laboratories, and others report notifiable events 資料產(chǎn)生外在變異 Produces extraneous variability in these data減少變異性以便： Need to minimize this variability to:監(jiān)視趨勢 Monitor trends評價干預效果 Evaluate the effectiveness of intervention activities地區(qū)間的比較 Compare areas比較結(jié)果應真實反應疾病本身的

3、變化和不同 Comparisons must reflect changes or differences in the disease疾病監(jiān)測的病例定義必須始終保持一致Case definitions for surveillance need to be consistent over time.報告病例數(shù)Reported Cases年份Quarter year20052006年某社區(qū)病毒性肝炎每周報告發(fā)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、區(qū)剔除社區(qū)醫(yī)院的病毒性肝炎每周報告發(fā)病率Viral Hepatitis for a county with and without one hospital, 2005-2006剔除社區(qū)醫(yī)院社區(qū)總報告發(fā)病率病例的錯誤分類可導致流行病學分析偏差Misclassified cases can bias epidemiologic analysis暴露Exposed病例 Cases非病例Not Cases合計Total真實True相似疾病Similar disease小計Total是 Yes 80201009001000否 No2020409601000合計Total1004014018602000

5、暴露組發(fā)病率 Rate in exposed 10%未暴露組發(fā)病率 Rate in unexposed4%相對危險 Risk ratio（RR）2.5危險差異 Risk difference 6%完美的病例分類則可給出不同的率Perfect classification gives different rates暴露Exposed病例Cases非病例Not Cases合計Total真實病例True相似疾病Similar disease合計Total是 Yes 800809201000否 No200209801000合計Total100010019002000暴露組發(fā)病率 Rate in exp

6、osed 8%10%未暴露組發(fā)病率 Rate in unexposed2%4%相對危險度 Risk ratio（RR）4.02.5危險差異 Risk difference 6%6%在消滅某種疾病X的過程中與其相似疾病的發(fā)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監(jiān)測到的疾病總數(shù)Total disease detected在消滅某種疾病X的過程中與其相似疾病的發(fā)病率等于1During elimination of disease

7、 X the incidence of similar disease = 1監(jiān)測到的病例總數(shù)Total disease detected疾病XDisease X相似疾病Similar disease什么是病例定義? What is a case definition? 一套標準 A set of standard criteria用于確定是否感染 Used to decide if a person has an infection保證衛(wèi)生統(tǒng)計結(jié)果是真實可信的 Assures that differences in health statistics are real 根據(jù)目的不同而不同 V

8、aries with the purpose不同專家會對同一（群）病人進行相同分類嗎？Will experts classify the same patients the same?10位專家會診100位病人 10 experts review 100 patients 每位專家均將他們劃分為某病病人或非病人 Each expert classifies them as a case or not a case of a disease X每位專家會按同樣方法對每位病人進行分類嗎？Will every expert classify every patient the same way? C

9、ase or not a case?是否可能存在完美專家？Will one expert be perfect?假設一位專家審閱100位病人的診療記錄 One expert reviews 100 patient records.他將如何判定病人與非病人？ A case or not a case of a disease X?一個月后同一專家重新審閱上述100位病人的診療記錄又將如何？ One month later the expert reviews the same 100 records.不同專家將會用同一方法或標準判定每位病人？Will every expert classify

10、every patient the same way? Case or not a case?一個典型的病例定義（臨床診斷）：麻疹A typical case definition: measles出皮疹37天 Generalized skin rash of 3 to 7 days duration體溫大于38度 Fever 38C加上以下一項或多項 Plus one or more of the following鼻卡他癥狀 coryza (鼻塞 stuffy, 流涕 runny nose)咳嗽 cough結(jié)膜充血 conjunctival injection敏感度和特異度Sensitiv

11、ity and specificity敏感度 Sensitivity 能夠發(fā)現(xiàn)的病例占所有真實病例的比例 of all the true cases of the disease how many (what percent or proportion) does the method discover?特異度 Specificity 能夠發(fā)現(xiàn)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?病例定義永遠不可能完美Case definitions a

12、re never perfect按病例定義判定By Case definition真實病例True Cases合計Total是 Yes否 No病例 Cases9020110非病例 Not cases108090合計 Total100100200敏感度等于真實病例被準確判定的比例Sensitivity = proportion of true cases correctly identified按病例定義判定 By Case definition真實病例True Cases合計Total是 Yes否 No病例 Cases9020110非病例 Not cases108090合計 Total1001

13、00200敏感度 Sensitivity = 90/100 = 0.90 = 90%假陰性率Percentage false negatives = 10/100 = 0.10 = 10%特異度等于非病例被準確判定的比例Specificity = the proportion of non-cases correctly identified按病例定義判定真實病例 True Cases合計TotalBy Case definition是 Yes否 No病例 Cases9020110非病例 Not cases108090合計 Total100100200特異度 Specificity = 80/

14、100 = 0.80 = 80%假陽性率 Percentage false positives = 20/100 = 0.20 = 20%假定某社區(qū)在疾病X暴發(fā)期間同時存在其它不同疾病Consider a county with different diseases during an outbreak of Disease X. 與疾病X相似 Similarity to disease X其它疾病Otherdiseases疾病XDisease X高度敏感的病例定義必將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 高度敏感的病例定義This is called a “highly sensitive” case definition非病例NotCases高度特異的病例定義必將排除包括很多真實病例A case definition that includes only cases will exclude many cases X疾病病例Disease X高度特異的病例定義This is called a “highly specific” case definition非病例NotCases病例定義可有多個水平The case definition may

16、have levels of certainty. 非病例NotCases疑似病例Suspect可能病例Possible臨床病例Probable確診病例Confirmed特異度 Specificity敏感度 Sensitivity細菌性痢疾暴發(fā)的病例定義Case definition for a shigellosis outbreak非病例NotCases腹瀉Diarrhea 2 daysDiarrhea 2 days+嘔吐Vomit 或者OR 發(fā)燒Fever 38CDiarrhea 2 days+Vomit 并且AND Fever 38CSuspect, orPossible, orPro

17、bable+實驗室陽性Shigella疑似病例Suspect可能病例Possible臨床病例Probable確診病例Confirmed敏感度和特異度可隨目標的不同而變化Variability in sensitivity and specificity depends on purpose診斷和治療 Diagnosis and treatment of patients.流行病學調(diào)查階段 Phase of an epidemiologic investigation確證暴發(fā)原因 To identify cause常規(guī)監(jiān)測或疾病登記 For routine surveillance or reg

18、istries內(nèi)部或者外部使用 For internal or external use暴發(fā)期間使用敏感病例定義During outbreaks the performance of a sensitive case definition improves相似疾病暴發(fā)疾病疾病暴發(fā)構(gòu)建病例定義Construction of case definitions疾病識別標志：Disease Identifiers: 癥狀 Symptomatology體征（物理檢查） Signs (Physical examination)臨床評價 Clinical evaluations (EKG, EEG, etc

19、.)不符合其他疾病 Lack of compatibility with other diseases治療情況 Response to treatment實驗室檢測（病毒分離、血糖等） Laboratory tests (virus isolation, blood sugar, etc.)流行病學標準Epidemiologic criteria時間 Time地點 Place人 Person宿主因素（基礎疾病） Host factors (underlying illness)與其它病例的流行病學聯(lián)系 Linkages to other cases相關危險因素 Associations wit

20、h risk factors感染性胃腸炎：病例定義示例Infectious gastroenteritis: Exle case definition臨床 Clinical:腹瀉（3次以上稀便x2天） Diarrhea (3+ liquid stools x 2 days) 發(fā)熱 Fever無其他原因（藥物抗生素） No other cause (drugs - antibiotics) 實驗室確診 Confirmed Laboratory:糞便中發(fā)現(xiàn)病原體 Organism identified in stool流行病學 Epidemiological在最短潛伏期內(nèi)住院 Hospitaliz

21、ed for minimum incubation period潛伏期期間在醫(yī)院 In hospital during incubation使用一個大多數(shù)或全部病例具有的癥狀特征Use one characteristic that will include most or all cases腹瀉 Diarrhea發(fā)熱 Fever黃疸 Jaundice出疹 Rash出疹并發(fā)熱 Rash+fever咳嗽并發(fā)熱 Cough + fever使用在某些病例中發(fā)現(xiàn)的更具特異性的癥狀特征Use more specific characteristics that are seen in some case

22、s特殊發(fā)現(xiàn) Specific findings楊梅舌猩紅熱 Strawberry tongue - scarlet fever特殊病癥 Pathognomonic finding柯氏斑麻疹 Koplicks spots = measles使用一組一般性的癥狀特征Use a group of common findings卡他癥狀 Coryza咳嗽 Cough結(jié)膜炎 Conjunctivitis其它標準Other criteria不能被其它已知疾病所能解釋的癥狀 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發(fā)熱持續(xù)5天或以上 Febrile illness for 5 or more days并同時具有以下5種癥狀中的4種 With four of the following five findings雙眼結(jié)膜充血 Bilateral conjunctival injection新發(fā)口腔粘膜破損 Oral lesions (new)手指和腳趾破損 Lesions on fingers and toes皮疹 Skin rash頸部淋巴結(jié)病 Cervical lymphadenopat

24、hy新生兒破傷風Neonatal Tetanus新生兒 Neonate who 出生時啼哭 Cried at birth出生后頭兩天內(nèi)能正常吸允 Had normal suck for first 2 days of life出生后第3天至30天以內(nèi) Developed from 3 to 30 days after birth無力吸允 Inability to suck出現(xiàn)痙攣 Generalized spasticity可有驚厥 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咳嗽持續(xù)2周或2周以上 Continues for 2 or more weeks陣發(fā) With paroxysms咳嗽后嘔吐 Posttussive vomiting病例定義應用實例Applying case definitions舉例：人狂犬病監(jiān)測病例定義的標準Exle criteria for a case definition for human rabies for surveillance臨床標準 Clinical:腦炎 Encephalitis發(fā)病后10天內(nèi)死亡 Death within 1

26、0 days of onset實驗室標準 Laboratory:頭發(fā)毛囊、角膜或者腦組織免疫熒光抗體染色陽性 Direct FA of hair follicle, cornea or brain抗狂犬病毒IgG或IgM抗體陽性（未經(jīng)免疫者） Anti-rabies IgG or IgM in an unvaccinated person流行病學標準 Epidemiological:被已知宿主動物咬傷 Bite from a known reservoir animal species被患狂犬病的動物咬傷 Bite from a rabid animal 舉例：狂犬病病例定義Exle rabi

27、es case definition疑似病例 Suspect患腦炎并于10天內(nèi)死亡 Encephalitis with death in 10 days可能病例 = 疑似病例 Possible = suspect and 動物咬傷 animal bite臨床診斷病例 = 疑似病例 Probable = suspect and被患狂犬病的動物咬傷 bite from rabid animal確診病例 =疑似病例、可能病例或者臨床診斷病例 Confirmed = suspect, possible or probable免疫熒光抗體檢測狂犬病毒 陽性 Rabies virus by direct

28、FA from cornea, hair follicle, or brain或者抗狂犬病毒IgM抗體陽性（未經(jīng)免疫者） Or anti-rabies IgM in an unvaccinated person根據(jù)以下報告的狂犬病例數(shù)據(jù)，哪些病例符合病例定義？Some data from reported rabies cases. Which fit the case definitions?E=腦炎encephalitisY = 是YesN = 否NoR =患狂犬病的動物 Rabid AnimalO= 其它動物 other animalND =沒有檢測 Not doneCI = 角膜印跡C

29、orneal ImpressionBr = 腦組織 Brain腮腺炎性腦膜腦炎Mumps meningoencephalitis臨床標準 Clinical腦膜炎或腦炎癥狀并發(fā)熱大于37.5度 Symptoms of meningitis or encephalitis with fever (37.5 C)腦脊液白細胞計數(shù)大于50個/ml、葡萄糖大于3,0 um/L CSF with 50 leucocytes/ml y glucose 3,0 um/L前2周內(nèi)患有流行性腮腺炎 Mumps disease within 2 weeks before流行病學標準 Epidemiologic發(fā)病前

30、一個月與流行性腮腺炎患者面對面接觸 過 Face-to-face contact with a mumps case in the month before onset實驗室確診 標準 Laboratory confirmation 抗腮腺炎病毒IgM抗體 Anti-mumps IgM 分離到腮腺炎病毒 Isolation of mumps virus流行性腮腺炎性腦膜炎Mumps Meningitis疑似病例 Suspect癥狀加接觸 Symptoms plus contact可能病例 Possible癥狀加流行性腮腺炎 Symptoms plus mumps disease臨床診斷病例 P

31、robable疑似或者可能病例加腦脊液檢查 Suspect or possible with compatible CSF確診病例 Confirmed上述三種病例 Suspect, possible or probable急性期或恢復期檢測到IgM抗體或分離到腮腺炎病毒 Anti-mumps IgM or isolation of mumps virus during acute illness or convalescence根據(jù)以下病例一覽表判定哪些病例符合病例定義Can you apply the case definition to this line-listing of patie

32、nts?病例一覽表Exle of a Line Listing1=“Yes”?=“Dont know”0=“No”ID #發(fā)病日期Date of SymptomOnset癥狀 Signs/Symptoms實驗室結(jié)果Labs人口統(tǒng)計學Demographics腹瀉Diarrhea嘔吐Vomit發(fā)熱Fever 101Positive stool culture年齡Age性別Gender11/2/0411?119M21/5/04010017M31/2/04010123F41/7/04111118?51/1/04?11118F如何制作一覽表How to Create a Line Listing及時添加新的確診病例 Add new cases as they are identifie