流行病学英文讨论课题目3课件.ppt

1、Discussion 2Clinical TrialsCohort studyCase Control studyPart 1 clinical trial1.1 Researchers conduct a randomized controlled trial to determine if Med A reduces post-operative pain more than Med B.The primary purpose of double blinding this trial is to avoid:A.recall bias B.selection bias C.confoun

2、ding bias D.non-random(differential)misclassification of exposure status E.non-random(differential)misclassification of outcome status1.2 The main benefit of a randomized controlled trial(RCT)compared to all other epidemiologic study design is that the RCT:A.is prospective thereby eliminating the ne

3、ed for historical data B.has better external validity C.guarantees that confounding bias will not occur D.tends to equally distribute into the study arms characteristics which may be independent risk factors for the outcome of interest E.tends to avoid random misclassification of the outcome of inte

4、rest 1.3 is a method that maximizes the probability that the two groups will be similar in background characteristics that may influence either the response to therapy or the primary outcome measure.A.blindingB.RandomizationC.diagnostic criteriaD.placebo-controlled trial.1.4 Fill the blank with”yes”

5、or“no”Knowledge of Treatment AssignmentBlindingPatient InvestigatorNoneSingleDoubleResults of the coronary artery disease(CAD)Therapy Trial Concerning the Risk of Developing MI Treatment myocardial infarction Medicine AMedicine B TotalYes9123114No287325612Total378348726n1.5 Calculate the risk of dev

6、eloping MI in each treatment group.n1.6 What is the percentage of risk of MI that would be avoided if Medicine B were used instead of Medicine A?n1.7 What is relative risk or rate ratio?How to explain its epidemiological significance?Part 2 Cohort study Case Control study2.1 when the incidence rate

7、of the disease is rare,what kind of study is most suitable to explore the underlying etiology?A Prospective studyB case-controlC descriptive studyD clinical trial2.2 For each of the following features,indicate whether it belongs to A for cohort study or B for case-control studybest for common outcom

8、esgood for rare outcomesrelatively inexpensiveoutcome is measured after exposureyields true incidence rates and relative riskssmaller numbers requiredmay uncover unanticipated associations with outcometakes a long time to completecontrols are selected on the basis of not having the outcomeoutcome is

9、 measured before exposure2.3 Indicate next to each statement below whether you consider it to be TRUE,or FALSEAn advantage of cohort study compared to the case control study is that cohort studies can directly estimate risks.The temporal sequence of exposure and disease can be directly addressed in

10、a cohort study as well as in a case control study.A disadvantage of the cohort study compared to a case control study is that in a cohort study one cannot address multiple outcomes.A disadvantage of the cohort study compared to a case control study is that in a cohort study one needs to follow a lar

11、ge number of participants if the disease is rare.2.4 Select the correct statement:na.)The attributable risk is the excess risk of disease in the exposed compared to the non-exposed during a defined period of time.nb.)The attributable risk is a ratio of the disease risk in the exposed compared to the

12、 non-exposed during a defined period of time.nc.)The attributable risk is a ratio of the disease risk in the non-exposed compared to the exposed during a defined period of time.nd.)The attributable risk is the prevalence of disease in the exposed minus the prevalence of disease in the non-exposed.ne

13、.)The attributable risk is the disease risk in a defined group at a specific point in time.Researchers investigated that 100 patients with bladder cancer and 600 patients without bladder cancer.20 of bladder cancer patients smoke,while 40 of without bladder cancer patients smoke cigarettes.2.5 What

14、is the study design?Calculate the appropriate measure of association for developing bladder cancer in smokers vs.non-smokers.2.6 Interpret the measure of association you calculated in question.nIn 1993 a case control study was conducted to assess a possible association between serving in the Gulf Wa

15、r in 1991 and the subsequent diagnosis of neurological diseases.nResearchers compared the military records of 750 Army soldiers seen for neurological symptoms at Walter Reed Army Hospital in 1992 to 1500 Army soldiers seen at Walter Reed Hospital the same year for non-neurological symptoms.nThe rese

16、archers used military records,which were accurately maintained by unit leaders,not the subjects themselves,to establish if each subject did or did not serve in the Gulf War.nThe study concluded that Army soldiers who served in the Gulf War had 50%more risk of having subsequent neurological disease v

17、s.those who did not serve in the Gulf War.2.13 The researchers only studied male Army soldiers.Select the best statement:A)The failure to study female Army soldiers is a possible source of confounding bias.B)Recall bias may have led to misclassification of exposure status.C)Effect modification by se

18、x may account for the observed result.D)Selection bias may have affected the result.E)Interviewer bias may have produced a random misclassification of exposure status 2.14 Subsequent analyses showed that the investigators often failed to identify subjects with mild neurological diseases among those

19、who did not serve in the Gulf War.How might this have affected the risk estimates?Choose the best answer.A.)It would have biased the estimate towards the null value of 1.0.B.)It would have biased the estimate away from the null value of 1.0.C.)It would have affected the studys external validity but

20、not its internal validity.D.)The effect cannot be reasonably determined based on the information provided.E.)It would have resulted in non-differential misclassification of exposure status.Summary nWhat is the difference between clinical trial and observational study?nAdvantages and disadvantages of

21、 clinical trial.AdvantagesDisadvantages Advantages and disadvantages of clinical trial Randomization tends to balance prognostic factors across study groupsSubject exclusions may limit ability to generalize findings to other patientsDetailed information can be collected on baseline and subsequent ch

22、aracteristics of participantsA long period of time is often required to reach a conclusionDose levels can be predetermined by the investigatorA large number of participants may be requiredBlinding of participants can reduce distortion in assessment of outcomesFinancial costs are typically highEthical concerns may arise Subjects may not comply with treatment assignments祝您成功！