率及其在现场流行病学中的应.ppt

1、a,1,率及其在现场流行病学中的应用,朱保平，医学博士，生物统计学硕士 中国现场流行病学培训项目美国常驻指导专家 ,a,2,100人的人群中有10例病人10 cases of a disease among a population of 100,a,3,发病数按地区分布 (1999) Incident cases by place, 1999,a,4,各地区发病数百分比 (1999) Proportionate Frequency Incident cases by area, 1999,a,5,病例数总是取决于人口基数The number of persons always determi

2、nes the number of cases,a,6,用率可以校正人口基数，让地点间的比较有意义We correct our comparisons by calculating rates that include the number of persons,a,7,病例数 = 人口数 X 率Cases = population*rate,a,8,比较发病或患病资料时，必须用率才有意义Rates are necessary to compare incidence data or prevalence data,Different areas Different times Differe

3、nt groups of people Different Exposures,不同地区 不同时间 不同人群群体 不同暴露因素,a,9,多数人群特征必须用率才能表达清楚Most person characteristics need rates for clear interpretation,a,10,比，比例Ratios and proportions,Ratio = x/y = one number/another Female/male or Female/All Proportion is a ratio in which the numerator is a part of the

4、 denominator x/(x+y) Female/all OR Female/(Female + Male,比 = x/y = 一个数 / 另一个数 例：女/男；女/总人数 比例是比的一个特例，其分母包含分子 x/(x+y) 女/总人数，或 女/(女+男,a,11,流行病学中的率Rates in epidemiology,Always a ratio Can be a proportion Population or substitute denominator Cases must come from the denominator Cases and denominator must

5、 be from same time period Usually has a time dimension,率一定是比的一种 可能是一种比例 其分母是人群数（或其替代值） 病例数总是从分母人群中产生 病例与分母人群一定来自同一时间段 通常有一个时间单位,a,12,流行病学常用的率有哪些? What are some common types of rates used in epidemiology,Proportion a/(a+b) Infected patients / total patients Ratio (a/b) Infected patients/ occupancy In

6、fections/total patients Person-time rate Infected patients / patient-days at risk Infected patients / device-days at risk,属于比例 a/(a+b)的率 感染病人数/总病人数 属于比(a/b)的率 感染病人数/床位使用数 感染数/总病人数 人-时率 感染病人数/病人风险天数 感染病人数/设备风险天数,a,13,患病“率” The prevalence “rate,Numerator = prevalent cases Denominator = population (or

7、population evaluated) at that point in time. Always a proportion Cases do not need to be identified at exactly the same point in time. Many academic epidemiologists do not consider this to be a “rate,分子=现患病例 分母=该时点的人群数（或所评价的人群数） 总是一个比例 病例不一定必须在一个确切时点找到 许多学院派流行病学家不认为这是一种率（因无时间单位,a,14,1998年9月30日时点患病率是

8、多少？*What is the prevalence “rate” on 30/09/1998,N = 100,a,15,罹患率The attack rate,A measure of risk Also called: Cumulative incidence rate Numerator: New cases appearing during an outbreak or epidemic Denominator: Population at the beginning of the period (outbreak or epidemic) Often expressed as % e.

9、g.: 8.7%, 87 per 1000,是描述危险度的一个指标 亦称“累积发病率” 分子：爆发或流行中发生的新病例总数 分母：爆发或流行开始时暴露人口数 通常以百分比表示（也可用其他单位） 例：8.7%，87/1000,a,16,二代罹患率The secondary attack rate,Numerator Secondary cases (among persons defined as contacts) Denominator All contacts at risk (exclude primary and co-primary cases,分子：二代发病数(在被定义为接触者中)

10、 分母：所有有风险的接触者(除外第一例及其同代病例,a,17,如图，甲肝从日托所向家庭接触者的传播。试问二代罹患率是多少？Secondary spread from a nursery to family contacts. What is the secondary attack rate,a,18,发病率The incidence rate,Numerator New (incident) cases appearing during a time period (usually one year) Denominator Average population during the tim

11、e period Midpoint population estimate Cases per 10X per year Example: 234 per 100,000 per year,分子： 新/发病例，在一段时期（通常一年）内发生 分母： 同期内平均人口数；或 该时期中点处人口数 用每年每10 x人口表示 例：每年每100,000人口 234人,a,19,1998年的发病率是多少？*What is the incidence rate for 1998,N = 100,a,20,分母应该多大才合适？What size should my denominator be,Try to ma

12、ke numerator a whole number The same as rates you will compare,让率成为大于1的数 与已发表的率具有可比性,a,21,人-时率：用它可校正每个病人暴露时间不同A person-time rate corrects for the time period that each patient was exposed,Numerator Incident (new) cases during period Denominator Time each person observed Totaled for all persons obser

13、ved More useful when Large variability in exposure periods Long time periods involved,分子 某段时间新/发病例数 分母 每人观察时间 所有人观察时间的总和 下列情况更有用 观察期间变异大 观察时间长,a,22,人时发病率（/1000人日）是多少？An example calculation of a person-time rate for individuals,发病率 = 2/267 = 7.5 病例 /1000 人日 Incidence rate = 2/267 = 7.5 cases/1000 per

14、son-days,a,23,计算人群组的人时数Calculate person-time for each year,计算人时：无病者 = 1人年； 发病者，失访者 = 1/2 人年 Count:disease-free persons = 1 person-year; persons with disease, persons lost to follow-up=1/2 person year,人时率 = 16/6400 = 2.5 病例 /1000 人年 Person-time rate = 16/6400 = 2.5 cases /1000 person-years,a,24,其他可以用

15、来估计率或危险度的比Other ratios that estimate rates or risk,Adverse reactions/doses distributed Injuries/vehicles registered Injuries/vehicle-kms Cases/representation of denominator,不良反应数/投放剂量数 伤害数/登记车辆数 伤害数/车辆-公里数 病例数/某种可用来代表分母的数值,a,25,发病率与罹患率比较Incidence rate and attack rate,An outbreak of hepatitis A in Gu

16、angzhou from March 1 to March 14, 2000 had an attack rate of 25 per 1000 The yearly incidence rate of hepatitis A in Guangzhou is 238 per 100,000 per year How do you compare these rates,2000年3月1日 - 3月14日间广州市发生甲肝爆发流行，罹患率为25/1000 广州市甲肝的年发病率为238/100,000 试问如何比较这两个率,a,26,是否真有甲肝爆发？Is there a Hepatitis A o

17、utbreak,Adjust population to make rates comparable Divide 238 per 100,000 by 100 = 2.38 per 1000 per year Adjust time period 2 weeks = 2/52 year 2.38 (2/52) = 0.11 per 1000 per 2 weeks 0.11 25, therefore outbreak is real,调整人群数，让两个率可比 将238/100,000 除以100 = 2.38/1000/每年 调整时期长短 2周 = (2/52) 年 2.38 x (2/5

18、2) = 0.11 / 1000 / 2周 0.11 25，因此确有甲肝爆发,a,27,用率比和率差来对率进行比较Rates may be compared with rate ratios and rate differences,率比=(甲率)/(乙率) Risk ratio = (rate a) /(rate b,率差=(甲率)-(乙率) Risk difference = (rate a)- (rate b,a,28,如何对几年或几个时期的发病率求平均值？How can I average an incidence rate for many years or periods,Mean

19、 rate Median rate Sum of cases/ sum of the mid-year populations,求平均数 求中位数 病例数总和/历年年中人口数的总和,a,29,死亡频度的测量Mortality frequency measures,Crude death rate Age-specific mortality rate Sex specific mortality rate Race specific mortality rate Cause specific mortality rate,粗死亡率 年龄别死亡率 性别别死亡率 种族别死亡率 病因别死亡率,a,3

20、0,1998年病因别死亡率是多少？*What is cause-specific mortality rate for 1998,N = 100,a,31,计算死亡率时分子与分母来源不同Mortality rates (ratios) with different denominator,Infant mortality rate Neonatal mortality rate Postneonatal mortality rate Perinatal mortality rate Maternal mortality rate,婴儿死亡率 新生儿死亡率 婴儿后期死亡率 围产期死亡率 母亲死亡

21、率,a,32,疾病严重度的测量Indicators of virulence,Death to case ratio Case fatality rate,死亡-病例比 某时期（年）病例数除以同期病例数 死亡（分子）与病例（分母）可能为不同人 病死率 病例中的死亡者比例 死者（分子）是出于病例（分母,a,33,病死率是多少？What is the case fatality rate,N = 100,a,34,1988 年死亡-病例比是多少？What is the death to case ratio for 1998,N = 100,a,35,出生统计指标 Natality measure

22、s,Crude birth rate Crude fertility rate Crude rate of natural increase Low birthweight ratio,粗出生率 粗生育率 粗自然增长率 新生儿低体重比,Manual 2 page 116, Table 2.13,a,36,死亡构成比 (PMR)Proportionate Mortality Ratio (PMR,Numerator Deaths from a specific cause (or cause-specific death rate) Denominator Deaths from all cau

23、ses (or crude death rate,分子 归因于某特定病因的死亡数 (或死因别死亡率） 分母 全死因死亡数 (或粗死亡率,a,37,在计算死亡构成比时，人口与时间被约掉了The population and time is lost from the PMR,OR,a,38,死亡构成比的用途Uses for PMR,Shows relative importance of specific causes within a population group To select problem for further epi study To determine priorities

24、 for health administration Limited usefulness Often misused Not a rate; comparisons are invalid,帮助显明人群中某特定病因的重要性 帮助择定需进一步研究的重要公共卫生课题 可帮卫生行政人员对公共卫生问题的重要性进行排序 用途有限 常被误用 不是率；互相之间无可比性,a,39,死亡构成比的缺陷Proportionate mortality: Deficiencies,Cannot compare populations Different areas Different times Different

25、sub-populations (e.g., age groups) Differences or changes in one cause affect value of other causes Excess in one yields decrease PMR in others Deficit in one yields increase PMR in others,不能对不同人群进行比较 不同地区 不同时间 不同人群组(如年龄组) 某一病因PMR的不同或改变影响其他病因的PMR 一个病因PMR过大会使其他病因PMR降低 某一病因PMR减少会使其他病因PMR增加,a,40,2002 年

26、一匹狼地区的各死因的死亡构成比Proportionate Mortality (PM) in Epiland, 2002,a,41,死亡构成比的排序受病因分类的影响Proportionate Mortality in Epiland,a,42,死亡构成比的排序也会受人时地分类的影响Percent of Total Cases of Disease X by Age, Epiland, 2002,a,43,一匹狼地区与多匹狼地区死亡构成比Proportionate Mortality, Epiland and Demiland,a,44,一匹狼地区与多匹狼地区死亡构成比Proportionate

27、 Mortality, Epiland and Demiland,a,45,一匹狼地区腹泻的发病构成比: 1995, 2000Proportionate (%) Cause of Diarrhea, Epiland, 1995 and 2000,a,46,那么，死亡构成比究竟有何用？Uses for PMR,Shows relative importance of specific causes within a population group To select problem for further epi study To determine priorities for health

28、 administration Limited usefulness Often misused,帮助显明人群中某特定病因的重要性 帮助择定需进一步研究的重要公共卫生课题 可帮卫生行政人员对公共卫生问题的重要性进行排序 用途有限 常被误用,a,47,潜在寿命损失年Years of Potential Life Lost (YPLL,Modifies the PMR for premature mortality One number summarizes premature mortality within a population group Places a higher value on

29、 younger age Uses an endpoint for age value 65 years for USA Life expectancy at birth Does not correct other problems of PMR,对死亡构成比就过早死亡进行校正 对人群组的过早死亡用一个数值来表达 在其计算中，年龄越小价值越高 假定年龄有个终值 在美国为65岁 或用出生期望寿命 它不能解决死亡构成比的其它问题,a,48,因车祸和肺炎死亡数Deaths from motor vehicle injuries and pneumonia,a,49,潜在寿命损失年的计算YPLL C

30、alculation,Sum ( 65 - age at death) For all deaths from a specific cause in persons under 65 years in a population For persons 65 years or older use 0 (zero,(65 - 死亡年龄) 对人群中所有65岁以下死于某特定病因者计算此差值，并对所有差值进行加和 对于65+岁者令其潜在寿命损失年为 0,a,50,潜在寿命损失年计算举隅YPLL Basic Calculation,a,51,计算因车祸死亡而造成的潜在寿命损失年Calculation o

31、f YPLL for motor vehicle injuries,a,52,潜在寿命损失率YPLL Rate,Compares YPLL for different populations Numerator: YPLL Denominator Population Population by age bands,用于比较不同人群的潜在寿命损失 分子：潜在寿命损失年 分母： 人口数 特定年龄段的人口数,a,53,危险度与率常被互用，但它们有不同点Risk and rate are often used interchangeably but there are differences,Ris

32、k: Cumulative probability of outcome Ranges from 0 to 1 (no chance of 100%) Example: 1 in a million chance of developing cancer in a 70 year lifetime,危险度： 某种结果（例如死亡）的累积概率 其范围总是在0和1之间（无法超过100%) 例：在70年生命历程中，发生癌症的概率是百万分之一,a,54,危险度与率常被互用，但它们有不同点Risk and rate are often used interchangeably but there are differences,Rate: Often has a time dimension Can exceed 100% Can be used to estimate risk if time period is short (e.g., annual) and disease incidence over the period is relatively constant,率： 常有时间单位 可以超过100% 如果时间区间较短、疾病发生率在该时间区间比较恒定，可以用率来代表危险度,a,55,归因比例（归因危险百分比）Attributable proportion (attribu