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1、,筛检,Screening,疾病自然史（Natural History of Disease）,目 录,概述 筛检试验的评价 筛检效果的评价,Introduction Evaluation of screening test Evaluation of effectiveness,Outline,筛检是运用快速、简便的试验、检查或其他方法，将健康人群中那些可能有病或缺陷，但表面健康的人、同那些可能无病者鉴别开来,Screening is defined as the use of quick and simple testing procedures to identify and separ
2、ate persons who are apparently well, but who may be at risk of a disease, from those who probably do not have the disease.,第一节 概述 Introduction,筛检试验流程图 Flow diagram of screening test,筛查方法的评价与选择程序 Procedures of evaluation and selection for screening test,金标准 (gold standard),目标人群 Target population,病人 P
3、atient,非病人 Non-patient,待评价筛查方法Screening to be evaluated,评价指标 Evaluation indicator,筛检试验 Screening test,识别健康人群中未被发现的某病患者或可疑患者，或高危个体 Screening is the detection of patients, suspected patient and high risk of the disease in healthy population,筛检试验 Screening test,问卷、常规体格检查、物理学检查、实验室检验、分子生物学技术 Questionnai
4、re, routine physical examination, physical examination, laboratory tests, molecular biology techniques,根据所用的筛检方法的数 量多少 单项筛检 多项筛选,筛检的分类 Categories of screening,Based on the on the quantity of screening methods Single screening Multiple screening,根据筛检对象的范围不同 人群筛检 目标筛检,筛检的分类 Categories of screening,Bas
5、ed on the scope of screening subjects Mass screening Targeted screening,简单性 廉价性 快速性 安全性 可接受性,筛检试验应具备五个特征 Five characteristics that screening test should have,Simple Cheap Quick Safe Acceptable,一级预防 二级预防 疾病的自然史 流行病学检测,筛检的目的,Primary prevention Secondary prevention Natural history of disease Epidemiolo
6、gical surveillance,Purposes of screening,筛检的疾病是当地一个重大的公共卫生问题 具备有效的治疗或预防方法,应用筛检的原则 Principles for the application of screening,The disease being screened should be a major problem Acceptable treatment or prevention methods should be available for individuals with diseases discovered in the screening
7、process.,有进一步确诊的方法与条件 该病的自然史明确,A suitable and effective test or examination for the disease should be available The natural history of the disease should be adequately understood,应用筛检的原则 Principles for the application of screening,该病具有较长的潜伏期或领先时间 预期有良好的筛检效益,The disease should have a recognizable cou
8、rse, with early and latent states of the disease being identifiable Expected good efficiency of screening should be available,应用筛检的原则 Principles for the application of screening,伦理学问题 Ethical Issues,尊重个人意愿 Respect for persons will 有益无害 Useful and harmless 公正 Fairness,一、筛检试验的评价方法 （Evaluation methods）
9、 确定金标准 (Determine Gold Standard) 选择研究对象 (Chose Study Subjects) 样本量的估计 (Estimate Sample Size) 整理评价结果 (Sort out evaluation result),第二节 筛检试验的评价 Evaluation of Screening test,金 标 准,所谓“金标准”是指当前 临床医学界公认的诊断 疾病的最可靠方法,Gold Standard,The best available test that is universally recognized by clinical medical cir
10、cles is called the GOLD STANDARD .,病例组 纳入各种类型的病人 对照组 最好选择需要与研究疾病鉴别的其他病人，即所选择的对照组与病例组具有许多相似的条件,研究对象 Study Subjects,Case group Include appropriate spectrum of patients Control group Need to be distinguished to the disease studied, that is the control has co-morbid conditions with case,样 本 量 Sample Siz
11、e,影响样本量的因素 待评价筛检试验的灵敏度 待评价筛检试验的特异度 显著性水平（） 允许误差（d）,Factors determine sample size Sensitivity of screening to be evaluated Specificity of screening to be evaluated Significance level（） Allowable error（d）,当待评价筛检试验的灵敏度和特异度均接近50 Both sensitivity and specificity of screening to be evaluated approach 50%,
12、n: the number of abnormal (diseased) or normal (healthy) patients in the study. : admissible error. P: the estimation of sensitivity and specificity for testing. ua : the u value for the cumulative probability equal to a/2.,当待评价筛检试验的灵敏度和特异度小于20%或大于80% Both sensitivity and specificity of screening to
13、 be evaluated less than 20% or greater than 80%,本来有病，被筛检为阳性,本来有病，被筛检为阴性,本来无病，被筛检为阳性,本来无病，被筛检为阴性,评价结果 Evaluation Results,评价结果 Evaluation Results,真实性（validity） 可靠性（reliability） 预测值（predictive value）,二、筛检试验的评价指标,Evaluation Index,灵敏度（sensitivity） 假阴性率（false negative rate）,真实性（validity）,False Negative Ra
14、te,Likelihood of a negative result when patient actually has disease,False Negatives,Sensitivity,Likelihood of a negative result when patient actually has disease,False Negative Rate,False negative rate increases with decreased sensitivity,False Negative Rate,Likelihood of a negative result when pat
15、ient actually has disease,特异度（specificity） 假阳性率（false positive rate）,真实性（validity）,False Positive Rate,Likelihood of a positive result when patient does not have the disease,False Positive Rate,Likelihood of a positive result when patient does not have the disease,False Positive Rate,Likelihood of a
16、 positive result when patient does not have the disease,False positive rate increases with decreased specificity,正确指数（Youdens index） （特异度灵敏度）1 1（假阳性率假阴性率）,真实性（validity）,阳性似然比(positive likelihood ratio，LR） 阴性似然比(negative likelihood ratio，LR）,真实性（validity）,真实性（validity）,一致率（agreement rate），符合率,一致率,真实性
17、（validity）,取值范围：-1和1之间,Range: between -1 and +1,Kappa值 = 实际一致性/非机遇一致性 观察一致性(Observation consistency) 机遇一致性(Opportunity consistency) 非机遇一致性(Non-opportunity consistency) 实际一致性(Actral consistency),真实性（validity）,标准差与变异系数 coefficient of variance，CV 符合率（agreement rate）,Agreement rate,可靠性（reliability）,影响可靠
18、性的因素,Determinants of reliability,Biological variations of subjects Variations in different observers Variations in different lab condition,受试对象生物学变异 观察变异 实验室条件,阳性预测值(positive predictive value) 阴性预测值(negative predictive value),预测值（predictive value）,灵敏度、特异度、患病率与预测值的关系,Relationship between sensitivity,
19、 specificity, prevalence and predict value,sensitivity and specificity in different blood sugar level,blood sugar SN SP blood sugar SN SP（mg/100ml） （） （） （mg/100ml） （） （ ）,80 100.0 1.2 150 64.3 96.1 90 98.6 7.3 160 55.7 98.6 100 97.1 25.3 170 52.9 99.6 110 92.9 48.4 180 50.0 99.8 120 88.6 68.2 190 4
20、4.3 99.8 130 81.4 82.4 200 37.1 100.0 140 74.3 91.2,Relationship between sensitivity and specificity,灵敏度与特异度的关系,非病人,病人,某项诊断标准的数值,截断点 Threshold,三、筛检试验截断值的确定 Determination of screening cut-off point,理想情况 Ideal situation,人数 Number,Normal,Disease,非病人 Normal,病人 Abnormal,某项诊断标准的数值,Cut-off,三、筛检试验截断值的确定 Det
21、ermination of screening cut-off point,实际情况 Actual situation,人数 Population,Screening tests use an arbitrary cut-off to separate two populations (normal vs. abnormal),a,c,b,d,a,c,d,b,Where cut-off is placed determines sensitivity and specificity,Screening tests use an arbitrary cut-off to separate two
22、 populations (normal vs. abnormal),Where cut-off is placed determines sensitivity and specificity,Normal,Abnormal,Few False Negatives High Sensitivity,- result,+ result,Screening tests use an arbitrary cut-off to separate two populations (normal vs. abnormal),Where cut-off is placed determines sensi
23、tivity and specificity,Normal,Abnormal,Few False Positives High Specificity,- result,+ result,Screening tests use an arbitrary cut-off to separate two populations (normal vs. abnormal),Where cut-off is placed determines sensitivity and specificity,Normal,Abnormal,Trade off between False and False +,
24、- result,+ result,Screening tests use an arbitrary cut-off to separate two populations (normal vs. abnormal),Test with High Sensitivity,Normal,Abnormal,A negative result allows you to rule-out whatever you are testing,- result,+ result,SnNout,Screening tests use an arbitrary cut-off to separate two
25、populations (normal vs. abnormal),Test with High Specificity,Normal,Abnormal,A positive result allows you to rule-in whatever you are testing,- result,+ result,SpPin,Screening tests use an arbitrary cut-off to separate two populations (normal vs. abnormal),用真阳性率和假阳性率作图得出的曲线，可用于 确定筛检试验的截断值。,A receive
26、r operating characteristic (ROC), or simply ROC curve, is a graphical is a graphical plot of the sensitivity, or true positives, vs. (1 specificity), or false positives, for a binary classifier system as its discrimination threshold is varied.,受试者工作特性曲线 Receiver operator characteristic curve, ROC,特异
27、度,血糖测定诊断糖尿病的ROC曲线,ROC curve for diagnosis of diabetes using blood glucose,第三节 筛检效果评价 Evaluation of effectiveness,一、收益 选择患病率高的人群 选用高灵敏度的筛检试验 采用联合试验 串联 并联,Yield To select the population with high prevalence rate To select the test with high sensitivity To design a combine test Series test Parallel tes
28、t,二、筛检的生物学效果评价 Biological effectiveness evaluation,病死率、死亡率、生存率,筛检组 Screened group,未筛检组 Unscreened group,比较,Fatality rate、mortality rate、survival rate,三、筛检的卫生经济学效果评价 Health-economic effectiveness evaluation,成本效果分析 Cost-effectiveness analysis 成本效益分析 Cost-benefit analysis 成本效用分析 Cost-utility analysis,领
29、先时间偏倚 病程长短偏倚 志愿者偏倚,Lead time bias Length bias Volunteer bias,第四节 筛检中的偏倚及其控制 Bias and Control,领先时间偏倚 （lead time bias）,领先时间：筛检诊断时间和临床诊断时间之差,Lead time: Interval between the diagnosis of a disease at screening and the usual time of diagnosis (by symptoms),Diagnosis by screening,Diagnosis via symptoms,Le
30、ad Time,Assumes survival is time between screen and death Does not take into account lead time between diagnosis at screening and usual diagnosis.,Diagnosis by screening in 1994,Death in 2008,Survival = 14 years,认为延长的生存时间是筛检诊断时间与死亡时间之差 没有考虑筛检诊断时间和临床诊断时间之间的领先时间,领先时间偏倚 （lead time bias）,Diagnosis by sc
31、reening in 1994,Usual time of diagnosis via symptoms in 1998,Lead Time 4 years,Death in 2008,True Survival = 10 years,Survival = 14 years,领先时间偏倚 （lead time bias）,病程长短偏倚 （length bias）,O Biological onset of disease,Y Symptoms Begin,D Death,P Disease detectable via screening,筛检 Screening,时间Time,恶性程度高 Aggressive,恶性程度低 Less aggressive,病程长短偏倚 （length bias）,志愿者（volunteer bias）,Type of bias where those who choose to participate are likely to be different from those who dont.,筛检参加者与不参加者之间，某些特征可能存在不同而导致的偏倚。,谢 谢 ！,