医药-临床-护理研究设计概览ppt课件

1、欢迎进入学习 课堂研究设计概览The aim of research should be to establish the truth and research design aims to minimise or exclude the threats to the internal validity of the study.There are only a handful of ways to do a study properly but a thousand ways to do it wrong. - Sackett (1986)偏倚Bias与真值的系统偏差Sackett DL.

2、Bias in analytic research. J Chron Dis 1979; 32: 51 常见偏倚选择性偏倚所选择的研究对象（样本）系统性地有别于所要推断的总体人群。例如志愿者偏倚、电话调查介入偏倚过多关照试验组导致疗效高估、病人依从性差导致疗效低估随访偏倚失访病人的特征有别于保持随访病人的特征失访可能与治疗有关知情偏倚医生如果知道病人接受何种处理将会影响他对病人病情的判断测量偏倚对所关心结局的判断带有主观性，则判断往往会引人而异混杂Confounding分组处理因素与所关心的结果同时受到另外一个因子（混杂因子）的影响 例如：大医院的病死率高于小医院 选择大小医院和病死率高低均与

3、疾病严重程度有关疾病严重程度即混杂因子随机化医学研究中的随机化平衡了比较的两组间显在的和潜在的混杂因素的影响，因此是控制混杂的重要手段在设计和分析时，可以采用分层或配对的办法对已知混杂因子进行控制但在分析时采用分层手法有一定的局限性，这时需依靠基于模型的统计方法予以解决。偶然性Chance由于存在偶然性，单纯随机化分组也有可能造成比较的两组间的不均衡样本数的不均衡某些混杂因子的不均衡关于研究设计统计学对医学研究的最重要贡献在于研究设计而不是数据分析从统计学角度出发的研究设计主要涉及研究的结构和数据收集过程的方方面面，包括度量的选择及其频数做适于研究目的的设计大多数研究只是想回答一些简单的问题，

4、但这并非意味它们的设计也是简单的没有合适的研究设计就不可能有意义的研究结果再多花一点时间在你的设计上吧。对所要研究问题的认识越深入、考虑的方面越多、越细，你的设计越接近于完美。研究设计的分类观察性研究（observational）还是实验性研究（experimental）前瞻性研究（prospective）还是回顾性研究（retrospective）纵向研究（longitudinal）还是横断面研究（cross-sectional）研究设计的类型ExperimentalProspectiveLongitudinalObservationalProspectiveRetrospectiveLon

5、gitudinalCross-sectionalLongitudinalCross-sectional处理/干预随机化设立对照设盲实验性研究之四大要素实验性研究的结构研究因子Factors研究因子的水平Levels均衡设计组内比较与组间比较析因设计Factorial designType of StudyAlternative NameUnit of StudyRandomised Controlled TrialsClinical TrialsCommunityInterventionTrialsPatientsCommunities/Groups/ClustersExperimental

6、StudiesClusterRandomisedTrialspopulationgroup 1group 2OutcomeOutcomenew treatmentcontrol treatment随机对照试验Randomized controlled trialsAdvantagesAbility to prove causal relationships is strongest of all study typesRandomisation minimises the risk of confounding variablesThe experimental design permits

7、greater flexibility, efficiency and powerful statistical manipulationDisadvantagesOften based on specific volunteer samples and findings may not be generalisable to the wider population Not feasible/ethical for major Public Health questions (e.g. Smoking and Lung Cancer)随机化Randomization防止选择性偏倚、控制混杂统

8、计分析的基础常用随机化的方法单纯随机化Simple randomization1. 抛硬币2. 利用随机数字表3. 利用随机数字发生器区组随机化Block randomization分层随机化Stratified randomization分层变量的选择。年龄、性别？、中心其他随机化方法整群随机化Cluster randomization观察性研究Observational study虽然实验性研究是推断研究因子效果的金标准，但是可行性和伦理性上的制约使我们采用观察性研究病例-对照研究Case-control study、定群研究Cohort study、横断面研究过去现在将来CohortCa

9、sesAndControlsCross-Sectional观察性研究With observational studies the investigator does not control the treatment or exposure but attempts to make valid comparisons between people with or without disease or between those naturally exposed or unexposed to a factor of interest.定群研究Cohort studiesCohort stud

10、ies entail observing two or more groups differing in exposure to a potential cause of disease overtime to compare the incidence of disease in each group.It is prospective with the exposure measured before outcome, enabling the direction of events to be established that is necessary if we want to say

11、 anything about causation.Only one risk factor can be assessed for each study but multiple outcomes can be measured.Typically these studies require large numbers, especially if the incidence of the disease/outcomes is low and a long time scale. Hence they are likely to be expensive.研究对象选择是否具有代表性失访失访

12、的性质（是否与结果变量有关？）其他问题习惯改变、工作改变偏重于高危人群调查病例-对照研究Case-control studiesWith case-control study the comparison is made between people with and without the disease in order to identify differences in previous exposures in an attempt to identify the cause of the event.Retrospective简单、成本低、适用于发病率极低的病种Multiple exposures can be assessed, and they are primary method of studying new or unusual outcomes.缺点对照难找（医院对照、健康对照）病例的确定回忆性偏倚Recall Bias匹配、匹配过度、一对多匹配横断面研究研究对象的选择应答率健康者偏倚因果推断因病致贫还是因贫致病？观察性研究的局限性The principal problem of observational studies is that although externally valid their internal v