横断面研究

研究生课程,1,Ch3 Research Methods of Epidemiology ()Descriptive study,研究生课程,2,Questions：,常住居民健康状况（常见/多发病、亚健康等）？疾病的早期筛检(screening)及诊断(diagnose)？医院感染(hospital infection)发生情况（分布特征）？可能存在的主要影响因素？采取措施后效果如何？如何合理安排医院各科的床位、医护人员等？患者对医院服务(hospital service)的满意程度？某慢性病(chronic disease)对患者生活质量(quality of life)的影响？关于社区获得性肺炎(Community-acquired pneumonia )？,研究生课程,3,Example,研究生课程,4,。,研究生课程,5,根据日常记录资料或通过特殊调查所得到的资料（包括实验室检查结果），对被研究人群的疾病或健康状况进行三间分布特征描述的研究，它是分析性研究的基础。,Concept of descriptive study,研究生课程,6,Commonly used data,demography datadeath datadisease dataother,研究生课程,7,【Characteristic】属观察性研究observation无须事先设立对照组no control不能分析暴露与效应之间的因果联系cannot analysis causal association,研究生课程,8,【Category】横断面研究 cross-sectional study生态学研究 ecological study常规历史资料分析 analysis of history data个案调查 case investigation病例报告 case report,研究生课程,9,概念特点研究目的与用途种类设计与实施优点与局限性,横断面研究cross-sectional study,研究生课程,10,横断面研究又称现况研究或患病率研究（Prevalence study） 是对某人群在某一时间断面的有关因素及健康状况进行的调查研究，从而客观反映有关因素与疾病的分布及二者之间可能存在的关系。,一、概念,研究生课程,11,属观察性、描述性研究无事先设立的对照组只能反映某一特定时点的情况因果并存，不能确定因果关系,二、特点,研究生课程,12, 了解疾病或健康状况的分布特征 了解分布特征与疾病之联系，提供因果线 索或建立病因假设 考核防治措施效果（重复横断面研究） 了解疾病现况，合理分配卫生资源 衡量国家或地区的卫生水平和健康状况 进行疾病监测，了解疾病的长期变化趋势 早期发现病人或高危人群,三、研究目的和用途,研究生课程,13,四、种类,普查（Census） 调查特定时点或时期、特定范围内的全部人群(总体) 抽样调查（Sampling survey） 随机抽样，调查特定时点、特定范围人群的一个代表性样本，以样本统计量估计总体参数所在范围,研究生课程,14,1、普查（census）目的：早期发现和治疗疾病了解疫情，早期预测疫情建立生理指标的正常值了解疾病或生理标准的地区、年龄、性别、民族、职业分布，为进一步研究提供线索,研究生课程,15,优点：信息全面，准确性好缺点：花费大，精确性难以保证；当患病率低、 或无简易敏感的诊断方法、无切实有效 的治疗方法时不适用适用症：应用原则(同筛检) 成本-效益分析后再确定,研究生课程,16,应用原则：检测手段灵敏、可靠被调查疾病的患病率较高（或是当地主要卫生问题）疾病进行性发展，自然史比较明确有较长的领先时间早期治疗有效，可明显改善预后,研究生课程,17,2、抽样调查（sampling survey） 优点：快速、高效、花费少、较为精确 缺点：信息存在误差（随机或/和系统的） 准确性不如普查；不适用于患病率低、 变异较大的情况；设计、实施及资料 分析较复杂 适用症：快速评价应用原则：样本具有代表性和足够量；调查方 法可靠,研究生课程,18,（一）研究目的（二）研究类型与方法（包括抽样方法）（三）研究对象及样本含量（四）资料收集（研究指标，调查表设计）（五）偏倚与控制（六）资料分析（统计方法、分析提纲）（七）可行性分析（人力、物力、财力等）,五、设计与实施,研究生课程,19,（一）明确研究目的（二）研究类型和方法,由研究目的决定研究类型和方法观察法与实验法普查与抽样调查抽样方法,研究生课程,20,抽样方法,非随机抽样non-random sampling 选择样本时，加入研究者主观因素，使总体中每个个体被抽取的机会不均等。,随机抽样non-random sampling 遵循随机化原则，保证总体中每一个个体都有同等机会被选入作为研究对象。,研究生课程,21,随机抽样方法： 单纯随机抽样（simple random sampling ） 系统抽样（systematic sampling） 分层抽样（stratified sampling） 整群抽样（cluster sampling） 多级抽样（multi-stage sampling）随机误差与系统误差（偏倚）样本大小的估计,研究生课程,22,目标人群 target population 纳入标准 样本大小估计 主观因素：值和（1-）值 抽样方法 客观因素：研究指标的变异程度 预计值（如患病率，阳性率等）,（三）研究对象,研究生课程,23,计量资料样本大小估计公式,计数资料样本大小估计公式,t:统计学上的t值 d: 容许误差 P：某病现患率 Q=1P,研究生课程,24,（五）资料收集,通过测定或检查的方法收集尽量采用客观、定量的研究指标和准确可靠的检测方法。直接用调查表询问研究对象,研究生课程,25,（六）偏倚与控制,偏倚是指调查或研究结果与真实情况不符，或样本统计量不能代表总体参数所在的范围，是一种系统误差。产生原因：,主观选择研究对象任意变换抽样方法调查对象不合作或因种种原因拒绝参加调查到的对象均为幸存者，无法调查死亡者回答不准确或回忆不清测量误差,研究生课程,26,严格遵照抽样方法要求，确保随机化原则提高研究对象的依从性和受检率正确选择测量工具和检测方法培训调查员，统一标准和认识作好资料的复查复核工作选择正确的统计分析方法，辨析混杂因素,偏倚的控制,研究生课程,27,（七）资料分析,检查资料的完整准确性，补缺、补漏，删除重复，纠正错误对疾病或某健康状态按规定的标准归类核实按不同空间、不同时间、不同人群描述分布特征和差异，进行显著性检验可按是否暴露于研究因素或是否有病进行分组，从而进行比较分析,研究生课程,32,优点： 1、样本来自人群，研究结果有较强的推广意义 2、调查人群中有自然形成的同期对照，具有可比性 3、可同时观察多种因素 4、无医德问题,六、优点与局限性,研究生课程,33,缺点及局限性： 1、疾病与因素同时存在，难以推断因果关系 2、只能获得患病率，无发病率资料 3、潜伏期或缓解期患者易被误诊而产生偏倚 4、一般只适用于对慢性病的研究 5、可产生选择性偏倚和信息偏倚,34,定义 目的 研究方法 优点 缺点,生态学研究ecological study,35,描述性研究的一种在群体水平上研究某种因素与疾病的关系以群体为观察和分析单位描述不同人群中某因素的暴露状况与疾病的频率，分析该暴露因素与疾病的关系,一、定义,36,提供病因线索，建立病因假设评估人群干预措施的效果,二、目的,37,生态比较研究ecological comparison study 观察不同人群或地 区某种疾病的分布，然后根据疾病分布的差异，提出病因假设 生态趋势研究ecological trend study 连续观察不同人群中某因素平均暴露水平的改变和 (或)某种疾病发病率、死亡率变化的关系，了解变动趋势，比较暴露水平变化前后疾病频率的变化情况，判断某因素与某疾病的联系。,三、研究方法,38,经济 ，出结果快提供病因未明疾病的病因线索在个体剂量无法测量时，是唯一可供选择的方法适用于研究因素暴露变异范围小，较难测量暴露与疾病的关系人群干预措施的评价及估计疾病发展趋势,四、优 点,39,生态学谬误 ecological fallacy 难以控制混杂因素存在多重共线性问题难以确定因果联系,五、缺 点,40,个案调查case investigation,对个别发生的病例、病家及周围环境进行的流行病学调查，多用于传染病及不明原因疾病的调查。通过流调，了解分析传染来源、接触者以及可能的传播途径掌握疫情，为控制疾病提供资料如：SARS流调,41,病例报告 case report,对临床上某种罕见病的病例进行详细的介绍，以引起同行的关注。有助于发现与识别新疾病或不良反应如：AIDS的发现有利于阐明疾病的发病与治疗机制如：“氟烷肝炎”有助于阐明疾病的罕见临床表现,42,横断面研究医学文献的评价原则1、文献中欲阐述的问题是否可用横断面研究？2、是何种横断面研究？3、采用了何种抽样方法？调查对象的代表性如何？4、调查是否在同一个较短的时期内完成？5、是否考虑研究中可能出现的偏倚及解决办法？6、所采用的研究指标及统计分析方法是否正确？7、研究所得出的结论是否客观？科学性如何？,研究生课程,43,Questionnaire Design,44,研究生课程,Elements of Questionnaire Design,Identifying the questionnaire contentWriting or selecting questions to measure variables of interestConstructing the questionnaire,45,研究生课程,A Questionnaire Is More than the Questions!,Other Elements Opening/cover pageInstructions (skip patterns, probes, optional wording)Introductions to questionsNeeded definitions and explanationsTransitions,46,研究生课程,Before Designing a Questionnaire,Decide the studys purpose (aims, research questions, hypotheses)Identify the variables to be measuredDevelop a preliminary analysis planDecide the data collection mode (e.g., interview, paper/pencil, computer-assisted),47,研究生课程,Make a Variable List,Write or obtain questions to measure the variablesUse existing measures whenever possible!Reliability and validity information may be available for existing measuresAllows comparison of results across studiesAllows estimation of trendsAdds to cumulative body of methodological experience with survey items,48,研究生课程,Objectives When Writing Questions,To get reliable and valid reports of respondents experiencesGood survey questions provide consistent (reliable) and accurate (valid) measuresWhen 2 respondents are in the same situation they should answer the question the same way.The answers to questions should correspond to what they are intended to measure.,49,研究生课程,Reasons Why Respondents Report Events with Less than Perfect Accuracy,They do not know the informationThey cannot recall it, although they do know itThey do not understand the questionThey do not want to report the answer in the context in which they are being asked it.,50,研究生课程,Considerations When Writing Questions,Type of question Response formatsQuestion wording,51,研究生课程,Types of Questions,Open-ended questionsClose-ended questionsOrdered response categoriesUnordered response categoriesPartially close-ended questions,52,研究生课程,Open-ended Questions,Responses are not provided to the respondent.Advantages:Researcher does not need to know universe of possible answersRespondent not influenced by specific alternatives suggestedRespondent can reveal what is most salientUseful in exploratory workCan be used to build rapport in interview,53,研究生课程,Open-ended Questions,Disadvantages:Effort required of respondentRespondents may vary in ability/willingness to articulateRespondents may be reluctant to reveal detailed information or socially unacceptable opinions or behaviorsLarge amount of information may be revealed, information may be vague or irrelevantDifficulties in recording and in reducing and coding material,54,研究生课程,Close-ended Questions,A list of acceptable responses is provided to the respondentAdvantages:Easier for respondentCommunicates same frame of reference to respondentsStandardizationLess variability in interviewer performanceLess time to administer and record response,55,研究生课程,Close-ended Questions,Disadvantages:Need to know appropriate response categories in advance Lack of spontaneity permitted respondentRespondent may be forced into an unnatural frame of referenceMay suggest response categories respondent has not thought ofRespondent may not feel as involved or motivated by questionnaire,56,研究生课程,Response Formats,Multiple categories that exhaust all meaningful answers and are mutually exclusiveDuring a typical work week (40 hours), how many hours do you spend on engaging in interpersonal relation:_less than 10 hours_10 to 19 hours_20 to 29 hours_30 to 39 hours_40 hours or more,57,研究生课程,Ordered Response Formats,Response categories are ordered along a gradient. Examples:Strongly agree to strongly disagree (3 to 7 point scale; include or not include a neutral response category)Excellent, Good, Fair, PoorNumerical rating scalesNoCompleteConfidenceConfidenceat All_ 1 2 3 4 5 6 7 8 9 10,58,研究生课程,Unordered Response Format,No single dimension underlies response categories. Respondent must evaluate each. Example:Which one of the following do you think is most responsible for the long waiting period in the emergency room of this hospital? (Choose only ONE answer.)Low staff moraleThe low priority given to the emergency department by the hospital administration.The low priority given to the emergency department by the medical staff.The large number of people using the emergency room.,59,研究生课程,Partially Close-ended Questions,Answer choices are provided and respondents have the opportunity to create their own responses. Example:What is your position at this school?Classroom teacherPrincipalGuidance counselorNurseOther position (Please specify:_),60,研究生课程,Question Wording - DO,Make the wording clear and unambiguous Use common vocabularyUse vocabulary appropriate for your audienceWrite questions like people talk not like people writeOnly include one idea per questionInclude both sides of the continuum in stemMake the frame of reference appropriate and explicit,61,研究生课程,Question Wording - DO,Use techniques for enhancing recall Shorten the reference periodUse landmarks to aid datingProvide a helpful contextProvide cues to stimulate recallAsk about typical behavior,62,研究生课程,Question Wording DONT,Use double-barreled questionsWhere do you go to get information about HIV risk and to exchange needles?When I get ill, I know it is because I have not been eating right or getting proper exercise.Can you tell me when you last visited the clinic?,63,研究生课程,Question Wording DONT,Use leading questionsDo you agree that all children should be covered by health insurance?With economic conditions the way they are these days, it really isnt fair to have more than one or two children.,64,研究生课程,Question Wording DONT,Use double negativesLack of immunization for smallpox is not a problem in the U.S.Most sex workers have little chance of not getting a sexually transmitted disease.Use discriminatory or culturally insensitive wordshusband/wife vs. partner,65,研究生课程,Question Wording DONT,Use incomplete wordingAge?What was your age on your last birthday?Reason lastWhat was the medical saw doctor?reason for which you most recently went to a doctor?,66,研究生课程,Question Wording DONT,Provide incomplete or overlapping response categoriesWhere have you received health care in the past 12 months?_Student health_UNC Hospitals_Private MD in Chapel HillUse check-all-that-apply format,67,研究生课程,Question Wording DONT,Ask respondents to make unnecessary calculations.Out of 100 students your age, how many to you think smoke cigarettes once a month?Use loaded questions or loaded wordsHave you ever shop lifted anything?,68,研究生课程,Practical Standardsfor Evaluating Questions,Is this a question that will mean the same thing to everyone?Is this a question that people can answer?Is this a question that people will be willing to answer, given the data collection procedures?,69,研究生课程,Constructing the Questionnaire:Putting the Questions In Order,Beginning inviting, interesting, non-threatening questionsMiddle most important, put difficult and sensitive toward endClosing easy questions again, often routine, background,70,研究生课程,Question Order,Psychological not logical orde