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clinical study design

the study of distribution and development of patterns of diseases epidemiology
"all research is descriptive and no research is better than its..." data
epidemiology looks for relationships between characteristics of a... population
variables that define study groups independent variable
outcome measures of interest dependent variable
in this type of study, you simply observe the occurrence of the outcome among the determined study groups. there is no manipulation of group characteristics, and no intervention observational
in this type of study, you manipulate exposures/group characteristics and follow study population for the outcome of interst interventional
in this relationship, you look at the exposure or characteristic, and then the outcome and whether or not they occur together but time is NOT a factor association
you look at the exposure or characteristic and then the outcome and whether they occur together, but time is a factor causation
what are the four types of observational epidemiological studies ecological, cross sectional, case control, cohert studies
what two types of observational studies are used for generating hypotheses ecological and cross sectional studies
this type of epidemiologic study is considered interventional randomized controlled clinical trials (RCCTs)
this type of observational study examines the entire population and is very broad. you collect population level data. ecological studies
ecological studies are sometimes called this correlation study
what are some advantages of ecological studies you can generate hypotheses, they're quick, easy, inexpensive.
what are some disadvantages of ecological studies no temporal relationship, no causality, cannot test hypotheses, ecological fallacy, late look bias
this is when you apply population level data to individuals ecological fallacy
this occurs in an ecological study for more severe cases of an illness, where fewer cases are identified because more people die sooner, so the results are disproportionalte late look bias
in this type of observational study, you sample a portion of a population an collect data. you look at associations between exposures and outcome. but it does not address causality, or determine incidence. you look at one "point" cross sectional study
what is the equation for prevalence of disease in exposed vs. non exposed individuals A/A+B vs. C/C+D
what is the equation for prevalence of exposure in diseased vs. non-diseased? A/A+C vs. B/B+D
what do cross sectional studies measure? prevalence
what are some advantages of cross sectional studies? can examine possible association between risk and outcome, relatively quick and easy; inexpensive, can generate hypotheses
what are some disadvantages for cross sectional studies? cannot assess causation, late look bias, not good for hypothesis testing
what are two observational studies for testing hypotheses? case control studies and cohert studies
what is the process for hypothesis testing studies? begin with observations, use control groups to test hypotheses about associations and possible. study begins with people with disease and compares them to people without disease, and compares the exposure status between these two groups.
what is one thing case control studies cannot do? measure incidence or prevalence of disease.
what are some challenges to case control studies? selection of controls (matched controles, hospitalized vs. non hospitalized, problem of "overmatching"), recall limitations, recall bias
in this type of observational study, study groups are arranged based upon exposure status and then followed for development of the outcome (disease incidence rates, mortality rates, etc). these studies can be prospective or retrospective cohort studies
in this type of cohort study, distribution is based upon subject's own life (ex: if they smoke or not, they get put into a particular group) prospective cohort study
in this type of cohort study, there is a difference in time aspect. you go back and look at records and see who gets disease and who does not. the study starts after everything has already happened retrospective cohort study
in cohort studies, do you look at risks, or oods? risks (specifically, relative risk)
what is the equation for relative risk? risk that exposed develops disease/risk that unexposed develops disease: A/A+B/C/C+D
when is an odds ratio a good indication for relative risk? when the disease prevalence is low
what are some disadvantages for prospective cohort studies? time consuming and costly; losses to follow up; can study only the risk measured at the beginning of the study
what are some disadvantages for retrospective cohort studies? recall limitations and bias. can only be used for common diseases
what are some advantages to cohort studies? both prospective and retrospective are flexible, can use to determine actual measure of risk, can study many disease outcomes, good for studying rare rksk factors.
this is a case control study within a cohort study. baseline characteristics are determined, subjects are followed over time, as cases develop, they are matched with controls, cases and controls are compared. nested case-control studies
this is the "gold standard" for studying interventions. you minimize bias in data collection; most scientifically rigorous. by definition, RCCTs ar eprospective studies randomized controlled clinical trials.
what is the difference between RCCFT and RCFT? RCFT focuses on preventitive interventions, and RCCT focuses on therapeutic interventions
a "blinded study" design helps to prevent this bias
in this type of blind study, subjects do not know to which group they have been randomized. the group identity (experiment or non-experiment) is unkonwn single blind
in this type of blind study, both subjects and investigators are blinded to group identity double blind
by definition, are RCCTs prospective or retrospective? prospective
what are some ways of enhancing the effect of randomization? decrease the influence of chance groupings that favor the possible confounding effects of variables other than the experimental intervention of primary interest, stratification of group independent variables, planned cross over designs
what do RCCT studies measure? incidence, prevalence, RR
what are some disadvantages of RCCTs? most expensive and time consuming. external validity (can the results be effectively generalized to a broader population?)
what are some advantages of RCCTs? most scientifically rigorous, can be least subject to bias (double blind studies)
what is the sequence of "hierarchy" of epidemiologicl studies from top to bottom? RCCT, cohort studies, case control studies, available data information, clinical observations
Created by: aferdo01